Genealogy is the study of families, family history, and the tracing of their lineages. Genealogists can range in skill level from amateur family historian to professional investigative geneticist. They can use a variety of tools including oral interviews, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members. The results are often displayed in charts or they can be written as narratives. The record of genealogical work may be presented as a “genealogy”, a “family history”, or a “family tree”.

The terms "genealogy" and "family history" are often used synonymously, but there is actually a slight difference in definition. A genealogy is used to establish information of a pedigree by pulling evidence, from valid sources, of how one generation is connected to the next and family history is a biographical study of the genealogically proven family, and of the community and country in which they lived. The field of family history is broader than genealogy, and covers not just lineage, but also family and community history and biography. Ideally, a detailed family history should only be conducted after the generational information has been genetically verified.

Technically a “genealogy” or a “family tree” traces the descendants of one person and a “family history” traces the ancestors of one person, but the terms are often used interchangeably. Descendants are the offspring that come after a person and ancestors are the generations of parents and grand parents that person came from. A “family history” also generally includes additional biographical information, family traditions, and the like, but the “family tree” could only include names. Most of the current genealogical formats are a combination of both.

The primary types of “family trees” found online are either genetic trees or genealogical trees. The Genetic Family Tree in actuality is an illustration of a concept rather than being an exact representation of someone's actual genetic family tree. It only includes ancestors that you have traced actual DNA from one of their direct descendants to confirm their relationship to you, whereas a Genealogical Family Tree contains all of your biological ancestors, DNA confirmed or not.

It's almost impossible to confirm DNA connections with all of your biological ancestors because of the way DNA is randomly passed down from generation to generation. It’s possible that you may not share any DNA with people you are genealogically related to because only bits of each parents genetic makeup is passed on to their children. As a rule we only receive 1/2 of our DNA from each parent so you will not have every segment that they inherited from their parents. since they also only received 1/2 of their DNA from each of their parents, some segments of DNA are lost in each generation.

This is very obvious when comparing your DNA with distant cousins. In fact, the more distant the generations are between cousins, the greater the chance that they may not have inherited the same pieces of DNA from their shared ancestors. It is possible that both you and your 2 or 3rd cousin have totally different segments of DNA from the same ancestors and won’t show up as a DNA match on the online Ancestry sites such as Ancestry.com or 23and me. It’s also possible that you didn’t receive any DNA at all from a really distant ancestor, thus you will have no direct DNA matches from any descendants of those ancestors. That, however does not mean that you are not related to them. Instead the relationship is considered a genealogical one, not a genetic one.

So knowing this, keep in mind when building a family tree that the Genealogical Tree, will include every ancestor that connects directly to you and their descendants, even if you have no actual DNA in common. The following Fan Tree can be filled in completely for a Genealogical family tree.

It may even include step and or adoptive relatives whereas, a Genetic Tree is a tree that contains only those ancestors who contributed to your DNA as verified by confirmed DNA matches with their direct descendants. Therefore there will likely be gaps in the tree that you will not be able to fill in, causing possible loses of entire populations of ancestors. In the following example of a Genetic Family Fan Tree, it only contains a small subset of your actual biological ancestors (where ancestors that DID provide DNA to your genome are shaded in gray): the ancestors in white are not represented in your DNA at all so you won’t have any direct matches through those ancestors, and any ethnicity results won’t include that ancestor. This is one reason why people who can trace their family lineage to populations such as Native American don't show any Native American in their ethnicity estimates when their DNA is analyzed. It does not mean the are not genealogically connected, but only that they didn't receive any genes from that ancestor, although a sibling may have.

It’s also important to note that the majority of the current online sites that process DNA are only comparing random sections of the DNA they process, generally decoding less than 0.02% of DNA. There are a few that offer a whole-genome test that compares the entire DNA makeup to others DNA , but they are currently to expensive for the general consumer market. The results of Genetic trees may improve once technology makes whole genome tests more affordable.