Mouse movement and cursor placement are usually expected to be consistent. Moving a mouse 1cm would normally result in a consistent cursor movement of, for example, 200 pixels every time the mouse is moved that distance.
Mouse acceleration is the setting where the cursor distances increases if the mouse is moved quickly.
Mouse smoothing or negative acceleration, is the setting where the cursor movement decreases if the mouse is moved slowly.
This setting is sometimes used to counteract a mouse with low sensitivity. A mouse with low sensitivity and mouse acceleration disabled may require multiple swipes across the mouse pad to move a longer distance. That same mouse with mouse acceleration enabled may only require one swift swipe to cover that same distance.
While the setting is a personal choice, it is recommend that you disable mouse acceleration to provide a more consistent aim in more competitive titles. While playing without mouse acceleration may initially be difficult for players used to playing with it, after playing without it for some time most players become used to it, and often may see an improvement in the precision of their aim.
If you want to be able to move the mouse around the screen with fewer swipes without enabling mouse acceleration, it is recommend that you pickup a gaming mouse with a high DPI sensor. This allows for the ability to move the cursor farther while keeping the cursor movement consistent.