I love illustrations and pratice so I guess this is a good explanation : learngitbranching.js.org/
You can find how rebase works but other things also :)

Rebasing is a tricky concept to grasp, as well as its consequences.

Lets try this metaphor.

Imagine a heavy metal chain. Each link in the chain is a git commit. Each link knows about the one before it.

Most non-rebase commands work by simply attaching new links to the chain.

Rebase, on the other hand, breaks one of the links, and then rebuilds a brand new chain from that point.

The reason this matters is that when you use git you're sharing the chain. When someone makes a mistake with rebase, you have to solve the problem that someone else threw away that shared chain created a new one and has thrown it at you.

This is why most advice you'll find about rebasing follows a golden rule of you can rebase things that you've not shared/pushed.

I'd highly recommend watching How Git Works by Paolo Perrotta on Pluralsight. There's a section on rebasing that I'll link to here, but it's best to watch the whole thing to pick up all of the background that makes this simple to understand: app.pluralsight.com/course-player?...

(A bit of a cop-out response, I know, but I think this course is OUTSTANDING and will do a much better job than me of explaining it)

rebase = re-apply the commits on this branch to a different starting point