One can say that stomp boxes follow UNIX philosophy. They do one thing and can be connected ("piped") to make complex sounds. For example, if you want distortion, with some modulation (say, some phaser) and a little bit of a delay, you could build a pedalboard ("pipeline") with those three units plugged one into another:

  guitar | distortion | phaser | delay | amp

BTW. in real life, as - by some weird convention - most of pedals have input in right side and output on the left, it looks like that:

  amp                                        guitar
   ^            .-- phaser <--.                 |
   |            |             |                 |
   `-- delay <--,             `-- distortion <--'