It lets the physics system take responsibility for motion, forces, gravity, velocity, and collision response.
Why a Rigidbody Exists
A Transform says where an object is.
A Rigidbody says how physics should move it.
That distinction is important. If an object is meant to be pushed, fall, bounce, collide, or be moved by forces, it usually needs a Rigidbody.
In 3D, that component is Rigidbody3D.
In 2D, the equivalent component is Rigidbody2D.
Rigidbody and Collider
A Rigidbody and a Collider solve different parts of physics.
The Rigidbody is the body that can move through physics.
The Collider is the shape used for contact.
In 3D, a typical moving object has both:
Rigidbody3Dsays the object participates in 3D physics motionBoxCollider3D,SphereCollider3D,CapsuleCollider3D,CylinderCollider3D, orMeshCollider3Dsays what shape it uses for collision
In 2D, the same relationship uses Rigidbody2D with 2D collider components such as BoxCollider2D or CircleCollider2D.
For many gameplay objects, the pair is what makes physics feel real.
When You Need One
Use a Rigidbody when an object should:
- move with velocity
- respond to gravity
- receive forces or impulses
- produce collision callbacks as a moving physics object
- be queried as part of the physics simulation
You may not need a Rigidbody for static scenery that never moves. Static colliders can still define walls, floors, ramps, or trigger zones.
Rigidbody Is Not the Visual
A Rigidbody does not draw anything.
The visible object usually comes from a ModelRenderer, primitive renderer, SpriteRenderer, or another rendering component.
The Rigidbody is about motion and physics behavior.