This question is especially for people who have joined in the last week. Have you used other fediverse platforms or is this your first time really using one? What do you think of it so far? Are you aware that you can comment on Lemmy posts with a Mastodon account?
I've been on Matrix and Mastodon for a number of years, but I'm new to Lemmy. Matrix is already better than competitors like Discord, in my opinion. It has a healthy pool of users including several major tech organizations.
I've never been too active on Mastodon for the same reason I never got into Twitter. I just don't enjoy "microblogging," and prefer mediums that are more oriented towards actual conversation. Lemmy does an excellent job in that respect.
It's just a protocol for sending data, depending on a client it could be a decentralised Discord (Cinny looks and feels very similar to Discord), WhatsApp, Google Hangouts, Guilded, Skype etc. Whilst most people use Matrix as alternative to Discord, you should know that it might be hard to get used to its flagship client, Element, because it doesn't resemble Discord much