Let’s look at some basics of using a mouse or other pointing device.
As you move the mouse pointer  from the root window onto other windows or menus, the shape of the pointer will change. For instance, on the root window, the pointer is a big X. The pointer may change to an hourglass shape to tell you to wait. When you resize a window, the pointer changes to a cross with arrows.
What’s “pointing and clicking”? That’s when you move the pointer to a place (usually over part of a window), then quickly press and release a mouse button (usually the first button). It’s the same idea as pressing a button on a telephone or another electronic appliance.
Something else you’ll do is “dragging.” That means moving the pointer to a place (such as the corner of a window), then pressing a mouse button and holding it down while you move the pointer. This is called “dragging” a pointer or object, because the object will be dragged along with the pointer until you let go of the mouse button.
Xterm windows have an advantage over plain UNIX terminals in that you can copy and paste text within a window or between windows. To get started, move the pointer inside an xterm window and select the window (set the focus there). Notice that the pointer changes to an “I-beam” shape. There’s also a block cursor. As you type, notice that text you input appears at the block-shaped cursor, just like it ...