Something I've wondered about every time I fly - how does gate checking of bags work? Does it differ per airline, or domestic vs international?

I have no status (I just don't fly often enough, and would rather switch airlines to get the cheapest fares than stay with one to gain miles), and I'm always worried that there won't be space for my laptop bag in the overhead bins by the time I board. It's normally full of all the gadgets I don't dare check in in case they get lost or stolen - if I had to gate check it, would it be safe? Does it go out on the carousel with the other checked bags, or do you fetch it from the FAs?