The Mirror modifier provides a parametric method of mirroring an object or a sub-object selection. You can apply the Mirror modifier to any type of geometry, and you can animate the mirror effect by animating the modifier's gizmo.
Mirroring a bench
To apply the Mirror modifier:
Represents the axis of the mirror effect. You can move, rotate or scale the gizmo to affect the mirroring. You can animate the gizmo transforms, which you can't do with the toolbar Mirror tool.
For more information on the stack display, see Modifier Stack.
Specify the axis or axes about which the mirroring takes place. You can usually see the effect in the viewport as you select the option.
Specifies the offset, in units, from the mirror axis. This is an animatable parameter.
Copies the geometry rather than simply mirroring it.