There are two main techniques used in project management: Critical Path Method (CPM) and Project Evaluation and Review Technique (PERT). CPM uses a single time estimate per activity and is deterministic, while PERT uses three time estimates (optimistic, pessimistic, most likely) per activity and is probabilistic. Both techniques involve showing the relationships between project activities in a network diagram. While CPM focuses only on time management, PERT can be used for both time and cost management of complex projects involving research and development work.