Float is a term used to convey schedule flexibility in different work sequences and is generally associated with a network diagramming method such as the Critical Path Method. Float is also known as Slack. It is used by project managers to help identify opportunities to adjust schedule for changing circumstances with the least impact to successor tasks or the overall project schedule.
Total Float refers to the amount of time an activity can be delayed before it threatens the project completion date.
Free Float refers to the amount of time an activity can be delayed before delaying the start of another activity in the sequence of work.