OK, so you can login anonymously. Great.

The real question is; why would you want to, given that the dead bird site is a cesspool of extreme rightwing awfulness? What are you hoping to learn or take from being on there?

No problem :)

It really depends on your intention…if you intend to just interact with (for example) Mastodon users that appear occasionally in the Lemmy communities you’re a part of then there’s no need at all. Or if you want to communicate occasionally with a Mastodon (or any other type of software) user then you could use their Mastodon handle to do so - for example go to the Search box on your Lemmy instance and type in @[email protected] (which is the ‘official’ Mastodon account on the mastodon.social server but it can be any handle) wait for a few seconds (or longer depending on the speed of the server) and the user account with the ability to private message them appears. There are currently some issues but it used to be possible to post directly to a Mastodon user’s timeline from Lemmy. Mastodon users can post to Lemmy. It’s worth remembering that Mastodon is a LOT more mature as a product than Lemmy, which is still in its infancy.

For now, at least, Id say if you’re looking to spend a lot of time on each different software type then register an account at an instance of it. The integration will come, but the fediverse is young, Lemmy in particular is very young so it’ll take time.

Lemmy is a piece of software. Lemmy software is a link aggregator - same as reddit.

So you’re signed up to a server that’s installed an instance (a copy) of the Lemmy software. Other servers also run the Lemmy software making them also instances of Lemmy. As well as you being able to talk to users in Communities (think subreddits) on the lemmy.world server, you can talk to users in Communities on other Lemmy instances. For example, lemmy.ml, feddit.de etc etc

KBin is also link aggregator software, just like Lemmy and Reddit. Same things apply there, same software on multiple servers, all able to talk with each other.

Mastodon software is a microblogging service - same as Twitter (and Threads). Just like instances of Lemmy, instances of Mastodon can talk to each other. So a user on mastodon.world can talk to (for example) a user on kolektiva.social which is also running the Mastodon software.

There’s also Pixelfed (Instagram), PeerTube (YouTube), Friendica (Facebook), Plume (WordPress) and a large variety of others.

Now, as well as all these different types of software (Lemmy, Mastodon, KBin, PixelFed etc) being able to talk to other instances of the same software on other servers, because they are all underpinned by a single method of passing information called ActivityPub, each type of software can also talk to each other - so you as a Lemmy user can also see posts and comments from a user on a server running an instance of Mastodon (or Plume, or PixedlFed, or…you get the idea). All these things are loosely joined together making a joined (federated) universe - the fediverse.