The number of standard slots on the rear panel that the controller occupies. This information is necessary in order to assess whether there is enough space in the case to install the board. Typically, controllers occupy
1,
2, or
3 slots.
This feature means that the controller board has a small height; and the height in this case is how much the board protrudes above the "motherboard" in which it is installed.
Low-
profile components are mainly designed for use in compact form factors where there is no room for full-sized boards. However, nothing prevents installing such a board in a larger case.