PERT and CPM are network techniques used for planning, scheduling, and controlling large and complex projects. PERT employs a probabilistic approach and uses three-time estimates, while CPM uses a deterministic approach and a single-time estimate. PERT is event-oriented, while CPM is activity-oriented. The slack concept is used in PERT, while float is used in CPM. Project crashing is possible in CPM but not in PERT.