Importance of Record Sources
There is a saying "Genealogy Without Documentation is Mythology". You will find that probably most of the individuals on your family tree will have "Facts", but NO "Sources" attached to them.
FACTS are the dates, places, and other information that has been entered for an individual, like the birth date and place, marriage date, death place and date, and so on. How would you know if the birth date and place are accurate?
SOURCES are the documents or documentation that actually shows that a birth, marriage, death, or other event actually happened. It is those sources that have become increasingly easier to find as more records come on-line.
Helpful links to explore: