This is such a big grab, I don't understand why they limit to inventions. Shouldn't they also demand assignment of all creative work so that if you write a novel on your own time and equipment they can collect all the royalties?
It's legalize. It depends on the language in the contract, but it usually includes everything under the sun, including creative works like books.
Sometimes there is a clarification for anything that can be related to your work, my current employer does that, but I've seen others without that. Which basically says they own you and everything you do or even think while employed by them.
Inventions is usually defined in the contract itself and does not necessarily apply to patentable things.
This is just my personal experience, so take it for what it's worth, though I do have a fair amount of experience with contracts and non-competes.
Some places do. I once worked for a UK business that was taken over by a US one. The difference in mindset between the original management team and the new one was nowhere more evident than in the one-sided IP terms they tried to introduce into everyone's contract and the laughable defence of this made by the corporate VP who was effectively taking over the top job. IIRC it was something about how they nurture their staff and deliver pots of gold to the end of their personal rainbows by unicorn ferry and all they ask in return is everything you ever create and your mortal soul, though the memory is fuzzy and it's possible that I added a couple of those details later.
This is one that drives me insane, and I just won't touch a company that is doing this as it is unreasonable and so evil to me. But sadly a lot of startup legal firms put this in their standard IP documents for employees to sign and if you don't catch it you can be screwed.