Automation envelopes are created when you activate the Automation write function (hence it is red)
It records any movements you make to any armed controls such as volume fader, pan control etc. When you next play the project back the controls will follow this automation.
It's a useful tool while mixing. A simple example would be to increase the volume of an instrument while it plays a solo and then reduce it again when it has finished the solo.
Just about any parameter can be recorded EQ controls, plugins, soft synths etc. Click on the track "W" or the one in the mixing module in the control bar to turn it off.
Use the Edit-->Delete function to delete it but make sure you deselect the other options in the delete dialogue though or you'll delete any data on the track as well.