Mastodon - my main social feed platform that first introduced me to the Fediverse in general.
Lemmy - my second main social feed platform that originally substituted Reddit from years ago.
Matrix protocol - communication platform I use to connect with users on the Lemmy instance I'm on
Peertube - would love to get an account going and use it more often but still don't know how but there's FediVideo.
Bookwyrm - Goodreads alternative that I signed up for that could use more work for a genuine reading tracker.
BONUS: my least favorite Fediverse platform lately
WordPress - because I used to run art blogs on there before I heard word about drama about the CEO of the corporation so I basically had to put out my last existing art blog...RIP.
I pretty much only use Lemmy but also contact friends and share photos on a Nextcloud instance one of them kindly provided (I assume it isn't federated though?).
I would really like to start using matrix but unless I host my own instance and get everything ready I'll never be able to convince my friends to switch, though some of them are slowly getting fed up with discord too.
I mostly use Discord for a few group chats, unixporn (please post more of it to Lemmy :3 !unixporn@lemmy.world) and some BG3 stuff. If the group chats moved to Matrix+Jitsi or even some form of Signal (that is still foss and does not require a phone number, self-hosted if possible) I would barely use Discord.
Edit because somehow I missed the most relevant part: I already barely get memes or trolls so not too many changes there.