PRJ meaning in File Type ?

A project (or program) is any undertaking, carried out individually or collaboratively and possibly involving research or design, that is carefully planned (usually by a project team, but sometimes by a project manager or by a project planner) to achieve a particular aim.

An alternative view sees a project managerially as a sequence of events: a "set of interrelated tasks to be executed over a fixed period and within certain cost and other limitations".

A project may be a temporary (rather than permanent) social system (work system), possibly staffed by teams (within or across organizations) to accomplish particular tasks under time constraints.

A project may form a part of wider programme managementor function as an ad hoc system.

Note that open-source software "projects" or artists' musical "projects" (for example) may lack defined team-membership, precise planning and/or time-limited durations.