Use of the Mouse Buttons

Use of the right-hand mouse button

Pressing the right-hand button completes a command, or the current stage of a command.
Holding down the right-hand button presents a window options and recent command repeat menu.

Use of the left-hand mouse button

Use of the left-hand button when rotate, spin or pan are selected from the toolbar, actions those commands.
For the use of the left-hand mouse button in connections with toolbars, see Moving Toolbar

At all other times pressing the LEFT button will make a screen digitise for ENTITY , FREE position or GRID position as appropriate.