These hinged momentary step switches are evocative of the 16-step sequencer keys on TR-808 synthesizers.
Also sometimes used on A/V equipment, they're very tactile, with a good clicky feel. And of course, the built in red LED is great for indicating when something is on or off - or as visual feedback when clicked.
There's four legs to the switch for mechanical stability. The switch is momentary SPDT type, there are two pins of the four that act as the common, and they naturally connect to one or the other of the remaining pins when the button is pressed. Check the diagram below to see which pins are the pole and which are the two throws. You may also want to use a multimeter on continuity mode to verify.
Note they are not breadboard or perf-board friendly! You'll need to either hand-wire or design into a PCB.
The LED is a simple 3mm, 20mA max, 2.1V-forward-voltage, red LED embedded into the plastic. There is no resistor built in so a 1K or so resistor will be useful to keep the LED from burning out. This LED guide will help you on how to pick a resistor - then you can PWM dim the LED from a microcontroller pin, or connect it to a digital output as desired.
Technical Details
Button dimensions: 17mm x 12mm x 14mm