These are small spring terminals. Open the aperature with the small arm, insert the wire, release the arm and the wire is held firmly in place.
This is a good quick way to to interface to bare wires. Capable of higher current and more resilient than breadboard or female header type connections.

Terminals with 0.1" standard spacing. Inserts directly into perf and proto board. Comes in 2, 3, 4, 5, and 6 positions. Rated up to 150V @ 2A. Terminal can accept 26 to 20AWG wire.

Documents: Datasheet