what happen when we use fixed joint

what happen when we join two gameobject using FIXED JOINT ? how it will affect on rigidbody.(both gameobject’s rigidbody).

@Jasmin1347 fixed joint generally attaches two gameobjects together at a certain distance,
If two objects are attached with a fixed joint movement of any one object will be restricted by other
For more details:
1.)FixedJointfromUNityManual
2.)fixed joint video tutorial