Each unconstrained component in an assembly has six degrees of freedom (DOF). It can move along or rotate about each of the X, Y, and Z axes. The ability to move along X, Y, and Z axes is called translational freedom. The ability to rotate around the axes is called rotational freedom.
Whenever you apply a constraint to a component in an assembly, you remove one or more degrees of freedom. A component is fully constrained when all degrees of freedom (DOF) are removed. You are not required to constrain completely any component in an assembly in Autodesk Inventor.