→Primary mouse button

a button of the mouse, usually the left mouse button, might also be identified as mouse button 1. The primary mouse button is the most commonly used button, for instance to select and drag elements. Compare: →Secondary mouse button
If you want to select an element (= click onto it), point to the element, then press and release the primary button. Double-clicking means to press and release the primary button twice. In order to drag an element, point to the element, click and hold the primary button, then move the element a new location and release the primary button.
Your operating systems provides options to reverse the mouse buttons. If you are left-handed, it is possible to use the right mouse button as the primary button.