Kinematics

Geometry of a mechanism.

Forward and inverse

Forward kinematics computes where the end lands given the joint angles. Inverse kinematics computes the angles needed to reach a target, and may have many solutions or none.

Degrees of freedom count the independent ways a mechanism can move.
Extra degrees of freedom allow reaching around obstacles.

Workspace

The set of reachable points has edges and interior regions the arm cannot enter. Planning a task starts with checking it lies inside that space.