From Joint Angles to a Point in Space
Forward kinematics answers a well-defined, always-solvable question: given a robotic arm's link lengths and current joint angles, where exactly does the end-effector end up in space? For a simple 2-joint planar arm, this reduces to straightforward trigonometry — the position of the first joint is determined by the base angle and first link length, and the end-effector position builds on that by adding the second link's contribution, rotated by the combined angle of both joints.
This is the direct, forward-only counterpart to inverse kinematics (see the Inverse Kinematics 2R Arm Calculator), which asks the harder, potentially ambiguous reverse question — forward kinematics, by contrast, always has exactly one unique answer for any given set of joint angles, since there's no ambiguity about where a specific, fully-specified arm configuration physically places its end-effector.
Visualizing the arm's actual geometric configuration alongside the calculated coordinates — not just reading out numbers — makes it far easier to build intuition for how changing one joint angle propagates through the connected link chain to move the end-effector, which is exactly the geometric relationship inverse kinematics has to solve for in reverse.