What is the difference between a milestone and a benchmark?

Answer

Milestones and benchmarks both represent events which have no duration in time. Milestones, however, are known as tracking – once linked, a start milestone will snap to the start of its earliest successor (unless an NLT constraint is applied earlier); a finish milestone will snap to the finish of its latest predecessor (unless an NET constraint is applied later). Benchmarks are not tracking – they remain fixed at their set date and are unaffected by logic. Furthermore, benchmarks are known as float throttles – rather than having float calculated to the project completion (or drift to the project start), a benchmark may be used to better allocate float to predetermined stages.