Located on Personal tab in Search Builder, this Condition searches one of several ways:
by an exact date in this format MM/DD/YYYY
by a day of month in this format MM/DD
or by just a month in this format MM
or by just a year in this format YYYY
The Group Comparison options are either Equal (an exact match) or Not Equal (does not match).
A few examples:
I want to find everyone born in 1972. Use the Comparison Equal and enter 1972.
Perhaps I want to find everyone with a birthday in August regardless of the year. I would still use the Comparison Equal and enter 08.
This condition is not the one to use when looking for people born before or after specific dates. For that, you would use the Condition Birthdate