What's the illuminated tact switches?

The illuminated tact switches is also called as illuminated tactile switches or illuminated tact buttons,it has momentary function and SPST circuit,it’s usually form with 6*6mm mini tact switch,and the operation force is 260gf;

but why we call it illuminated momentary tact switches?The illuminated tact switches utilizes the centre space of button and built into a led indicator,the led pin terminal is indepent with switch pins,if you wanna illuminate the tact button,you need to connect the LED terminal and distinguish the anode and cathode and control the voltage of the LED,because different led color with different voltage.