What is path planning?
Path planning as the name suggests is the ability of the robot to plan a collision free path from its current location or configuration to a goal configuration.(See figure below)
What are the main classifications of planning algorithm?
Path planners are broadly classified as follows
Geometric Planners: Geometric planners compute paths that are collision free. They incorporate the size of the robot while computing collision free paths
Kinematic Planners: Mere geometric plans do not entail their execution since the robot kinematics may not permit them to do so. For example a geometric planner for a car may compute a path that allows for lateral motion of the car as long as it is collision free. However a car cannot move laterally since its kinematics prevent it from doing so.
Dynamic Planners: During motion on rough and uneven terrain the terrain ground interactions play a crucial role in determining the feasibility of a kinematic and geometrically consistent path. Planners that consider the dynamics of the vehicle and plan paths that are dynamically feasible are considered dynamic planners.
What are the prominent geometric planning algorithms?
Geometric planning algorithms have their roots in computational geometry. The popular algorithms include the visibility graph computed over a configuration space, the vornoi diagrams , cell decomposition methods  and grid based gradient descent methods