What is a bypass and is it related to plug-ins' automation only?

Bypass temporarily disables a plug-in without losing any settings you've made in it. It's not just related to Automation, you can Bypass any plug-in down in the Smart Controls panel by clicking on the little power symbol in the left side of the plug-in slot. With Automation, you can have an effect set up and Bypassed, and then Automate it so the effect happens only at certain parts of the song (like, maybe, an echo effect that only kicks in during the choruses)..

Well, I find a bypass button, but I only have two choices there, e-piano and channel eq. If I choose a bypass, then how can I use it? Where are appearing the choices, on which I can use a bypass? And why the channel eq turned a grey? Video is included. https://youtu.be/NYYg_ebBuII

It's very simple -- if there's an effect on a track and you want to temporarily turn it off, Bypass it with that that button. When it turns grey it's Bypassed and you're not hearing that effect. If you change your mind you can click it again [as you did in the video] and the effect will turn blue and you'll hear it.