What's the difference between git switch and git checkout <branch>

Well, according to the documentation you link to, its sole purpose is to split and clarify the two different uses of git checkout:

• git switch can now be used to change branches, as git checkout <branchname> does
• git restore can be used to reset files to certain revisions, as git checkout --<path_to_file> does

People are confused by these different ways to use git checkout, as you can see from the many questions regarding git checkout here on Stackoverflow. Git developers seem to have taken this into account.

git checkout is a bit of a swiss army knife in that has several unrelated uses.

If you modify a file but haven't staged the change, then git checkout <filename> will reverse the modifications... a quick and easy way to cancel changes to a file. You remain in the same branch.

git checkout <branchname> (as you noted) switches branches.

Two completely different purposes, which could lead to confusion if a file name and a branch name are similar.

Having it as two commands is clearer.

switch has some limitations: at the moment you can switch from any commit to <branch name>, however it's impossible to switch from <branch name> to a particular commit with a status of detached HEAD. So you need to use git checkout 5efb (where 5efb is an example of a hash reference to arbitrary commit)