Earlier quoted context omitted.
A very general difference is being paid for your labor vs your thoughts. People paid for their labor are paid by the hour and get overtime. People paid for their thoughts usually get paid per year, and don't get overtime. I guess the general idea is that you are always thinking, so how would it be possible to decide when you are or are not on the clock? (Obviously this is a generalization with lots of exceptions, it'…
I do not like that line of thinking! Per your view, the employer can then claim your "thoughts" outside of the office as their "property". Anytime someone puts a[n] employment agreement that claims right to all my intellectual output while employed I say "Thanks, but no thanks."
Yah, and in fact that is exactly what they do. Usually they make you give them a list of any prior inventions you already have, and they claim ownership of everything else.
Obviously you can negotiate and not sign it, but it's pretty typical clause.