Width of containers using Bootstrap...?

I’ve just attempted the first beginning project (Tribute Page).

My project is on CodePen here:

I can’t understand why my About paragraph taken up the whole width of the screen, whilst the other containers are much narrower. I’m sure this is a noob question, but I can’t see anywhere where I’ve inputted anything to make that so…?

What I was actually trying to achieve ideally was a floating full width title bar with the rest of the content also full-width.

Okay, I worked it out. I confused myself with container vs. container-fluid. D’oh