Explaining stuff, especially the world is in the case of Fanfiction only really needed in case of a heavy AU with a lot of changes, or if you write the Fanfiction in a way that even Fandom outsiders can read it well. Yes, those exist. I write mine like this, but that's more to practice for my original works.

You need to avoid to just info dump the reader with a wall of text that isn't advancing the progression of the story. That is rather boring to read and may be just lazy writing.

Maybe you could sneak in a few tidbits of info in descriptions.

"[...] like many other Tarranians, her hair conforms to her form of magic. As a plant mage, she has hair as blue as her birth month flower."

Or

"The attacker pulled out a rather big dagger, maybe even a small sword of sorts. The ink blue blade, shaped like a scythe moon marking the thief as a warrior of the Karrian, a race known for their special blue metal."

It of course works with descriptions of scenery as well. But you also, if you really need to dumb info, use the setting. The setting is a school? Why not having the characters sit in history class and talk, without the teacher noting. Have them listening on the side.

Maybe you can use this as well to introduce a characters goal. The teacher talks about a war, ended by a group of warriors, the main character is intrigued and wants to join this group. The teacher talks about their deeds. Or, also because of said war, the culture has adapted a behaviour, like the dislike of people with a trait, like magic.

Exposition dumps, meaning that the author just tells the reader straight up a ton of information, without reason, are annoying. They stop the flow of the story which makes the dry exposition even more boring. Avoid texts that don't progress the plot. You need to find a way to show or tell the reader organically what they need to know. Use the setting, but avoid to just dumb info. Sure, there are some unavoidable situations, like the cliché of finding a cave with an explanatory text or picture, probably of a prophecy and a character reads it out loud.

A good way of doing so was in 'Harry Potter and the Chamber of Secrets', (I know J. K is a cunt), in which Hermione is petrified and the boys find her note about Basilisks and the tubes. Not perfect, but it isn't too much, it is organically build in and still progresses the story. It doesn't pause the events and just tells.

This example is also why I think writers should read a lot, to see how other writers solve things, to see what to do or not to do, to find inspiration. But I don't say to copy other folks, especially when you write original works.