Front panel switches - what did they do?

Since I'm an igmo about most machines before the mid-eighties (and still fuzzy even on most of those), I'm curious about all these older machines with front panel buttons and switches. What all did they do? You could actually program them using the front panel right? Some of them bootstrapped this way, too? What kind of "language" was used for that (ie.. what were the basic mechanics)? Did the buttons ever change color? Were you considered a badass if you had switch flipping all memorized down to an art? Were they mainly multi-position toggle switches or on/off buttons? They just seem to be a lot more important on older mainframes and minis. Also, what was the main reason for the blinkenlights? Was it to show system load or specific system states? Just curious. I'm learning a ton from reading these threads on older machines, but there is so much I don't know. -Swift