A pay period is the stretch of work each paycheck covers. The two most common schedules sound alike but behave differently. Biweekly pays every other week on the same weekday, 26 times a year. Semimonthly pays twice a month on fixed dates, usually the 15th and the last day, 24 times a year. Weekly and monthly schedules exist but are less common for salaried jobs.
The yearly total is the same either way; the check size is not. A $96,000 salary is $3,692 gross per biweekly check and $4,000 per semimonthly check. The biweekly checks are smaller because there are two more of them.
Biweekly has a quirk that matters for budgeting. Two months each year contain three paydays instead of two. If your monthly bills are built around two checks, those third checks are free money in the best sense: they can fund a goal, a sinking fund, or an extra debt payment with no change to the routine. Semimonthly has no such months, but its paydays line up neatly with rent and other first-of-month bills.
The common mistake is budgeting biweekly pay as if it were monthly by multiplying one check by two. That undercounts income by about 8% and leaves the three-paycheck months unplanned. Allocate builds the calendar from your actual paydays, so safe to spend runs from this check to the next one, not from the first of the month.