This is an RP-SMA-P (male) connector. If you have a board with a standard SMA connector and would like to connect to external 2.4 GHz antennas with RP-SMA cables without an adapter, then you can use this connector to replace the existing SMA plug. Some benefits of doing it this way is that you won't have to go through the hassle and added cost of using an adapter and you'll probably get slightly better performance since an adapter could add some RF power loss to the system due to an impedance mismatch.

Datasheet