@urbanbirdbud that's alright! // instances are basically tiny pods that connect to the larger mastodonverse. everyone has to be on an instance to connect to them. for example, i'm on mastodon.social (i think you are too!) we can reach out to each other via looking ourselves up on tags.
people from all instances can interact with each other, unless an instance is blocked by another (eg. blocking pawoo.net i think? for child porn posting) we can't see their users or content that way.
@urbanbirdbud being on a different instance from another user also means you can't follow them, sadly! but if you want to be available across multiple instances, you can create multiple accounts at different instances using the same email address; i think this is specifically because account data is instance-related, so feel free to multiaccount if that interests you! if it doesn't, you can also redirect/move your account on one instance to another you've created on another instance.
if you're looking at tags, instances shouldn't matter too much aside from following people. however, since each instance has their own federated/local timeline, you may find posts that could be alienating (eg. being on tabletop.social when you're not a tabletop player).
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