Rotataion gates will rotate a qubit around the axes of the Bloch Sphere. The three gates Rx, Ry and Rz will rotate respectively around each axis.
Rz gate is similar to the S and T Phase Shift gates but allows you to set an arbitrary angle to shift the phase.
Each gate can be represented by a unitary matrix, by replacing the θ with the appropriate angle you want to rotate.
|cos(θ/2), -i(sin(θ/2))|
|-i(sin(θ/2)), cos(θ/2)|
|cos(θ/2), -sin(θ/2)|
|sin(θ/2), cos(θ/2)|
|exp(-iθ/2), 0|
|0, exp(iθ/2)|
While Rz is similar to S and T gates, Rz gates can also introduce amplitude changes along with phase changes, unlike S and T gates that only produce a phase change.