A bezel is the outside frame around a computer tower or monitor. On a computer case the bezel is the front area of the case where devices protrude through the case. On a CRT computer monitor, the bezel is the outside frame area around the monitor glass. It's a bit of plastic that makes the server look less like the metal box of bits it actually is.
The bezel is attached to the front side of the server and it protects the hard drives and the power button from removal or accidental usage. The bezel comes with a key and a lock but it's not necessary if the server itself is only accessible by you or your administrator staff.
Our bezels fit and are designed for these servers.