Written records are the foundation of genealogy research, documenting the vital events in an individual's life, from birth to marriage to burial. They also provide data on property ownership, military service, taxation, school attendance, census enumeration, memberships, and other important aspects of day-to-day life.
These records, whether created by governments, organizations, or private institutions, are where you'll find many of the details about your ancestors. Documentary evidence of your relatives may also be found in other, less “official” sources, including newspapers, photographs, tombstones, family Bibles, school yearbooks, church membership lists, and even oral family histories.
A digital image that has been scanned or created from an original source is generally considered by genealogists as equivalent to the original as long as no evidence suggests that the image has been manipulated or altered, other than to enhance readability. Thus, there is generally no need to view both the microfilm and digitized version of the same record, unless there's a legibility issue or something appears to be missing.
The sources you'll encounter in your genealogy research can generally be classified, according to the Board for Certification of Genealogists (BCG), as either original or derivative. These are a little different than the terms “primary source” and “secondary source” that you may be used to, because they refer to the physical form and provenance of a document or record, not the information that it contains.
An original source is one that exists as it was originally recorded. Examples might include an oral recorded history, a handwritten will, a baptism recorded in the church records, a diary, or a photograph.
A derivative source is produced by reproducing some or all of the content contained in an original source. Photocopies, abstracts, extracts, transcriptions, databases, indexes, and authored works such as genealogies and histories are generally considered to be derivative sources, as is most information found on the Internet. Examples include a transcript of an obituary, a database of marriage records, or a published genealogy.
Whenever possible, it is best to view the original source. Each time a record is transcribed, copied, or manipulated in some way there is a chance for errors to creep in. Handwriting can be difficult to interpret. Typographical errors are easy to make. Vital information can easily be skipped by accident or left out because it isn't considered important.
How reliable is information found on the Internet?
The majority of the records you'll deal with will be derivative sources, but this doesn't necessarily mean they are unreliable. It is best, however, to consider such information as a clue for further research, and not a statement of absolute fact. Look for a citation to the original source from which the information was derived so you can evaluate the source for yourself.
Most genealogists use the terms “primary” and “secondary” to classify information, rather than sources. This is because any single source may include both primary information and secondary information.
Primary information is generally provided close to the time of an event, by someone with firsthand knowledge of the reported fact(s). A birth date recorded on the birth certificate by a doctor or parent present at the birth is an example of primary information.
Secondary information is provided by someone with secondhand knowledge of the reported fact(s) or is information that was recorded long after the event occurred. A birth date recorded on a death certificate by a child of the deceased is an example of secondary information. This doesn't mean the information is incorrect, just that there is more of a chance that it could be.
Each fact or piece of information found within a source needs to be evaluated separately to determine whether it is primary or secondary. This classification doesn't refer to the accuracy of the information — it refers to the likelihood of its accuracy. The quality or weight of the information should also be further assessed based on who provided the information, knowledge of the informant, and how closely the information correlates with information provided by other sources.
Secondhand information is often correct. And firsthand information can sometimes be inaccurate. A group of people who experienced a car accident firsthand, for example, will often tell slightly different versions of the story. In another case, a couple may have moved back their marriage date by a few months when they recorded it in the family Bible, to cover up an illegitimate birth.