Rather than fixed hole(s), a brush faceplate features two sets of brushes for cabling to pass through from the socket backbox. They are most often used for low-voltage wiring of devices and appliances like HDTVs, stereo systems, soundbars, and speakers.
The main advantage of a brush faceplate is that they avoid the need to fully terminate cables at the wall. Instead, the brushes neatly conceal a more rough-cut hole where the backbox sits. They allow various sorts of cables and wires - power, HDMI cable, audio, SCART, coaxial - to pass through, holding them loosely but tidily.
This is handy for electrical devices you might want to move around from time to time, or don't want to anchor with a fixed termination at the wall. As well as making installation far quicker and easier, fewer connections mean reduced potential for signal loss, interference or instability.