I'm using the Thunder app to access my lemmy.world account. Is Mastodon also Lemmy? Can I browse lemmy.world and mastodon at the same time? I'm so new and vv confused.
They're both fediverse, but one is designed to follow communities, and the other is designed to follow people. A Mastodon user sees a community as a user, and can thus subscribe to it. There's not really a way for a Lemmy user to do the inverse and subscribe to a user.
If you want a platform that does both (can subscribe to both communities and users), check out Kbin.