In addition to showing geographic ancestry percentages, some direct-to-consumer DNA tests also include insights about physical traits like hair and eye color. With 23andMe, this trait information is mostly available in the upgraded Ancestry + Health kit, but some interesting tidbits can be found in the Your DNA Family report, which is available if you opt to participate in the DNA Relatives service. 
Every human carries two copies of the genetic code, one inherited from the mother and one from the father, some 6 billion letters in all. Apart from identical twins, no two individuals have the same genetic code.  With the exception of the egg and sperm cells, all the cells of our bodies have 23 pairs of chromosomes, 46 in all. One chromosome of the pair is inherited from the father and one from the mother. However, in males the 23rd pair consists of a so-called Y-chromosome and an X-chromosome, whereas females have two X-chromosomes.  The Y chromosome contains a gene which triggers embryonic development as a male and carries information about the male’s paternal lineage.
Men have an X and a Y (chromosome) that are paired together. Women don’t have the Y, they just have two X’s. A child’s genes come from a mix up and recombining of the two parents. So a girl child will still end up with two X’s but some bits of them will come from the father’s X and some from the mother’s. A boy child on the other hand may have some bits of X from both mother and father, but his Y will have just come purely from his father – virtually unchanged. That makes Y-DNA such an exciting possibility for genealogy where you want to follow the paternal (surname) line. You could expect that Y-DNA will therefore pass virtually unchanged from father to son through the generations, meaning that the Y-DNA of a man’s g-g-g-g-grandfather will look very much like that of his own Y-DNA – with some little changes.
Guidelines recommend that women with a BRCA1 or BRCA2 variant should be screened for breast cancer earlier and more often. Risk-reducing surgery or medication may also be offered. Men with a variant should be screened for breast cancer. Screening guidelines for prostate cancer vary. This test is not a substitute for visits to a healthcare professional for recommended screenings. Results should be confirmed in a clinical setting before taking any medical action. It is important to talk with a healthcare professional before taking any medical action.

Although, I have absolutely no British or Irish ancestry, I found my results extremely satisfying. I particularly appreciate that living DNA gives you a lot of ways to view your data. You can see your ancestry results as color-coded dots filling up a person’s silhouette, on a map, as a pie chart or on a timeline. All the graphics present the same set of data, but each has its own appeal. Within each graphic, you can also choose to view global or regional matches and cautious, standard or complete estimates, which each have a different level of detail and certainty.
The reason that saliva works as well as blood (or hair follicles or skin samples) is that your DNA -- which is short for deoxyribonucleic acid -- is present in all of them. It's the basic genetic code present in all of your cells that makes up your key attributes, from the color of your eyes to the shape of your ears to how susceptible you are to cholesterol.
For our evaluations, we assembled a group of testers willing to spit into a tube on camera. We chose four individuals of varying backgrounds. Two had previously taken one or more DNA ancestry tests, and two had not. Two had fairly well-documented family histories to compare against, one was adopted, and one had information about one side of the family, but not the other. All of us took DNA tests from AncestryDNA, 23andMe, National Geographic and Family Tree DNA. One tester also took each of the five additional tests we reviewed. 
The SGM Plus system of DNA analysis targets ten loci, each of which contains two alleles. These are the “short tandem repeats” that vary between individuals. In addition, a further locus is targeted that acts as in indicator of the sex of the donor. A “full” DNA profile is one in which all of these loci have produced a reliable and reportable result. Occasionally, the processes used to target some of these loci fail, resulting in an incomplete or “partial” DNA profile. The most common reasons for such failure are either that a very small amount of DNA was present in the sample, the DNA may have become degraded, or that substances may have been present in the sample that may have inhibited the analysis process. Depending on the degree of success of the DNA analysis, the match probability calculated from a partial DNA profile may be reduced below the 1 in 1 billion that would be obtained from a full profile.
Good explanation, but I was a little distressed by the part of the analogy that says people know what work to do because "someone tells us." That statement makes people sound like robots and that we do not make decisions on our own. Maybe this is lost on me because I work for myself, but this paints the picture of a chain of people telling other people what to do and everyone following blindly. Something to think about when discussing this concept with children! Humans have free will... :)

Some concerns about the ultimate efficacy of certain home tests seem to emanate from the industry itself. I did a telomere-measuring test (a mouth swab) by Titanovo, based in north Colorado, which came back saying that my telomeres were too short, putting me at 10 biological years older than I am. However, when I contacted Titanovo, it explained that it had stopped telomere measuring and was now concentrating exclusively on its DNA-utilising “bioinformatics” health, fitness and wellbeing website (analysing client data from other genetic testing sites).
Three of the companies, MyHeritage, Ancestry and FTDNA, use the Illumina OmniExpress chip and 23andMe uses the new Infinium® Global Screening Array chip from Illumina. The fact that all of the chips come from the same company may be confusing, leading some to believe that all tests are created equal. This is not the case. The chip used to process DNA samples is only one part of the process. Each company develops their own analysis of the results, references different population samples and provides different reports. In addition, each one of these DNA test providers offers different tools for you to analyze the data you receive, creating variations in results, accessibility and usefulness.

Autosomal DNA Tests: These type of tests have become extremely popular over the last couple of years as prices have dropped and the amount and accuracy of the results has increased. Autosomal testing looks at information across the genome to provide clues to our personal ancestral history on a much broader scale than either mtDNA or Y-DNA testing can. While this type of genetic testing is an ever evolving science, you can expect to get a general breakdown of your ancestors’ geographical origins (your admixture) as well as connections with people who share your ancestry. This can be a unique and exciting way to tear down those brick walls and uncover branches of your family tree you never knew you had. For some, the results can be surprising and enlightening–for others, there can be a simple verification of already known information and even some disappointment in discovering nothing new.
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