A split transaction allows you to attribute a single transaction to different causes or programs. For example, a constituent gives you a check for $1000 and wants $750 to go towards a philanthropic project and the other $250 to got towards scholarships. There is no need to enter two separate transactions, the single transaction can be entered and "split" into the appropriate For, Fund, Event, and Appeal. A transaction may be split as many times as necessary, as long at the total adds up to 100%.
Switch the Split Transaction button to "Yes" and click on the "add icon", the small blue box just below the Split Transaction button. Enter the appropriate For, Fund, Event, Appeal, and Fundraising Goal Category for each amount.