All mouse clicks are clicks with the left mouse button unless otherwise specified.
The left mouse button is used primarily for selection. It also enables other tasks when used in conjunction with other keys on the keyboard. To select an entity, with Select Mode active, point to the entity and click the left mouse button.
Window Selection - when in selection mode, hold down the left mouse button and drag a window over the desired geometry to select all entities that touch or are within the window.
Zooming - hold down both the Ctrl key and the left mouse button and then drag the pointer over an area of the graphics area to zoom in on that area.
The mouse wheel is also a button that can be clicked in the same way as the left and right buttons. Simply press on the wheel without scrolling it to middle-click.
If your mouse has a wheel it can be used for the following functionality:
Panning - press and hold both the Ctrl key and the middle mouse button while dragging the mouse to adjust the vertical and horizontal position of the drawing within the graphics area.
The right mouse button is used to access shortcut menus in various locations in the user interface.
Rotating - hold down Ctrl and the right mouse button while dragging to rotate the view in the graphics area.