in different social networks I often see a table of fediverse alternatives to centralized social networks like twitter = mastodon and so on, but I noticed that the alternative to reddit is piefed and not lemmy, can someone explain what kind of fediverse project this is, and is it different from lemmy?🤔
ActivityPub is the fediverse protocol, lemmy and piefed are software implementations of that protocol.
In a similar way, email is a protocol, and Gmail and Exchange/Outlook are software implementations of that protocol. You can use Gmail to send email to Outlook users. Different people can administer their own Exchange servers on their own domains.
And some features of the software work best with other people who use the same version of the same software, although most things kinda work between different software. Like how calendar invites sometimes act weird between users of different software, but for the most part the core functions work OK.
So lemmy and piefed (and mbin and sublinks and some others) are different software trying to speak to other fediverse services through the ActivityPub protocol. It mostly works, but some of the details don't work exactly the same between each type of software.