Try checking out the Studio One reference manual for more information regarding "Automation".
Automation lets you record changes in parameter values; thereafter, Studio One can perform these value changes for you. For instance, you can record level changes in a Track by capturing your fader movements during playback; from then on, Studio One can perform the level changes.
Before the advent of automation, mixing was very much a performance. Sometimes it took many pairs of hands on the mixing console to accomplish all of the fader, mute, solo, and other movements to achieve a mix. Automation makes it possible to record the mixing performance in any way you desire and endlessly tweak every parameter until the desired mix is achieved.
In Studio One, automation is recorded in automation envelopes, which are a series of data points connected by lines that represent the changing values of the parameter being automated.