A planning language for writing states, actions, and goals.
PDDL is like a board game rule sheet for a robot. It shows the start, legal moves, and how to win.
You meet it in robots, games, and delivery planning. A planner reads it and finds a valid plan.
Planning
PDDL describes the world and the goal for a planner.
STRIPS
PDDL inherits and extends the STRIPS way of writing actions.
KR
PDDL writes states, actions, and goals as symbols a system can reason with.
Symbolic AI
PDDL belongs to the symbolic AI tradition for planning.