@butterflybean absolutely!
Fediverse is a slang term for "Federated universe" which is generally described as any software that uses the protocol called ActivityPub that carries content across websites.
So Fediverse = All ActivityPub softwares.
Mastodon, is one of MANY softwares that use the ActivityPub protocol. It has a "Twitter-like" UI.
However, you may have heard of Pixelfed, it has an "Instagram-like" UI and only supports media posts.
Peertube is like YouTube and only supports video.
There are others that do other things as well and they can all mostly be seen and interacted with via your mastodon account because of ActivityPub!
To do this, if you find a Pixelfed post on a Pixelfed site that you'd like to interact with, just copy the link to the post and paste it into the search bar of your Mastodon instance.
This works for every post that comes from an ActivityPub software.
Sorry for the long winded post but I am VERY passionate about Fediverse and hope you like it here.
I really hope this helps and isn't too confusing. Let me know if you have any more questions!😁