That's called a trackball. The device stays in place and you move the ball (usually) with your thumb, rather than moving a mouse which in turn moves the ball inside (or with the newer optical mouse, electronically senses the mouse motion).
Track Ball Mouse
A tracker ball is both a the ball on top of a stationary mouse and a type of a mouse that has a ball on top. A typical mouse is moved over a pad and has the ball directing the cursor on the bottom, but a tracker ball type mouse has the ball on top of a stationary mouse where you direct the cursor by moving the ball with your thumb, FOREFINGER AND MAINLY WITH YOUR PALM. This type of mouse is sometimes called a tracker ball for short and the ball on this type of stationary mouse is also called a tracker ball. [ delete the following:...It is not a good name. What does it track? Nothing that I can tell. Computer terms were assigned by people who wanted to make it confusing, didn't speak English, or were very confused themselves] It would be better explained as follows. '''A tracker ball is both a the ball on top of a stationary mouse and''' [?a type of a mouse that has a ball on top]. '''A typical mouse is moved over a pad and has the ball directing the cursor on the bottom, but a tracker ball type mouse has the ball on top of a stationary mouse where you direct the cursor by moving the ball with your thumb,''' '''forefinger but mostly with the inner aspect of your palm. This type of mouse is used by people with arthritis or RSI as it saves making the fiddly and speedy movements with the digit joints (which cause some people pain) and directs the cursor by making a round movement after putting your hand over the large glass "tracker" which is on top of the "mouse". I myself was able to work as a secretary doing 100wpm until the age of 59 despite arthritic fingers since my late-40s, because an ERGONOMIC TRACKER MOUSE was recommended and purchased for me by my employers. I can highly recommend the TRACKER MOUSE to anybody - especially to those with arthritic hands and intermittent RSI.''' '''"Tracker Lover"'''
If the ball is on the bottom, it's a "roller ball." If it's on the top and meant to be touched, it's a "trackball."
A trackball is similar to a mouse but has a ball located on the top rather than on the bottom. Trackballs are used to move pointing devices on computers and are frequently used with CAD workstations.
A trackball.
what is roller ball mouse
The device with a rolling ball on the top is called a computer mouse. It is used to move the pointer on a computer screen by rolling the ball and is an essential tool for navigating and interacting with the computer.
mouse ball
A track ball mouse is a mouse that uses an internal ball to track movement, instead of a laser. These have been outdated by optical mice.
break the mouse on the outside
Generally an optical mouse provides much better function than an older ball design mouse. The lack of an internal ball to move the mouse reduces the need for cleaning and build up do to the ball itself wearing down.
Well the mouse sends the movements of it to the computer. A mouse with a mouse-ball has rollers inside of it that move with the ball and from there can operate similar to a keyboard. An optical or 'laser' mouse is much more advanced.