/home is a directory ("folder"). Inside that directory, there's one subdirectory for each user, where you're expected to keep your personal files, configuration files, user data from software (e.g. save games from your games), stuff like this, personal data.

And Linux allows you to mount any partition in any directory of your choice.

Because of those two things, a lot of people create a partition and mount it as /home. So if something bad happens with the distro, and you need to reinstall it, ~~your princess is in another castle~~ your data is in another partition, safely stored. It's usually a good idea, but in your case it's a bad idea - because your /home/[insert username] directory from one distro will be likely the same as in the other distros, so they'll interfere on each other, and software user data will become a mess.

Instead, what I recommend you is to not create a /home partition. Let each distro have its own /home. However, do create a partition to store your data, and mount it inside your /home/[insert your username] directory. That way you can access all your files from all your distros, but the software user data won't be mixed.