mastodon stuff via Lemmy?

I'm fairly new to the fediverse, but my understanding is that different platforms are supposed to be able to share content between them. I have always hated most social media and reddit was the only one whose layout I could stand, so my favorite fediverse platform is Lemmy. I do have a mastodon account but if I can get the same content here I'd rather just delete it and use a platform I like. Is that how it works? If so how do I do that/know when I'm doing it?