Many times a particular event, such as a marriage, may have several, sometimes conflicting, sources. Regard your genealogy work as a legacy that you will leave for future generations to admire. You want to document each of the facts that you record so someone in the future can check your sources and evaluate the veracity of the information Genealogists divide sources into two basic categories, Primary and Secondary sources. Primary sources are those which were generated in close proximity to the event, for example a baptism entry in a parish register or a birth certificate. Secondary sources are those which were compiled by someone from primary or other sources, for example a family history or even the date and place of birth listed on a person's death certificate, which might be based on the recollection of someone present at the latter event.
Secondary sources are more likely to suffer from transcription or research errors.
None are immune, however. My own birth certificate incorrectly shows as the location of my birth the home of my parents, rather than grandfather's home where I was actually born. In a case of discrepancies like this, it is even more important to document the sources, such as eye witnesses, of the facts that you are recording. During the course of your initial gathering of information be alert for leads to other potential sources. If a relative has served in the military, been a member of a union or professional organization, applied for a trade or professional license, received an academic degree, there is likely to be a paper trail that may have significant genealogical information such as date and place of birth, where he or she was a resident at a particular date, etc.