What is a Plex "bundle", and why would it need to be "cleaned"?

Would like some context on what this even means.

all your metadata, subs, images for an item or show goes in a ā€˜bundle’.

As you move and change so changes the bundle, dead stuff in a bundle needs to be cleaned - and I have no idea how any of this works - but a clean bundle is a happy bundle.

I do know, sometimes, in order to ā€˜change’ something in a bundle - you have to drop a Thermo-Nuclear Weapon on it with this:

So as far as bundles, and the cleansing of them, I would make myself familiar with the practice - because you WILL need it at some point. Guaranteed.