With toe clips, the third part of the system, the part that fits onto your shoe soles is called a cleat. This is a slotted bit of metal or platic which engages with the lip of the pedal to ensure a rock solid attatchement. It was only ever used by racing cyclists or really athletic tourists, never by everyday commuters. It prevents rapid disengagent of the foot , hence racing cyclists saw the immediate advantage of clipless systems.

Clipless systems also use cleats on the shoe sole but this is a quite different thing that engages the quick-release mechanism on the pedal.

Track riders use all kinds of hybrid systems including clipless pedals with additional straps for security.

One of the few manufacturers who still make a wide variety of quality traditional pedals are MKS.