Hey everyone. There's been an influx of users over the last 2 days as a certain website has restricted access to their API forcing apps to finally shut down.
TLDR: Welcome! You can search for communities across all instances with tools like this and this or create a community for your interests right here. For mobile apps: here is a list of choices. Don't worry about not having everything down pat and don't be shy about participating here and elsewhere.
If you're new to Lemmy it may be a little confusing at first but that shouldn't deter you from participating.
Firstly, take a moment to read Demigodrick's post if you haven't yet and are confused about how federation works in general or about how to search for communities outside of this particular instance.
On our instance, anyone can create a Community and become its moderator by default. It takes very little effort to create but requires a little bit of commitment to looking over it. You can always choose to remove yourself as moderator (and ideally hand it off to someone else) or delete it completely if needed.
There are useful tools for searching for existing communities such as: https://lemmyverse.net/communities and https://browse.feddit.de/
While there is no problem with having 'redundant' communities across instances as each can host its own discussions, it may be a good idea to search for a community before creating it as you may find a group that has already done some of the legwork for you.
Right now we have a couple niche game and tech related communities that are steadily growing but don't feel restricted to that. Any topic is fine as long as it adheres to the general instance rules.
Most people lurk but you'll find that the general vibe is fairly positive and accepting on Lemmy so don't hesitate to comment or post even if it's not something you usually do because the barrier to entry for content is fairly low as places grow (as long as it's not extremely low effort/spam).
As for browsing, do know that you can block communities that you do not want to see to have them drop out of the 'All' feed (no option to block entire instances on a user-level at the moment but hopefully that comes soon. It currently has support so it's just a matter of someone implementing it).
I personally like to browse All and Subscribed and sort by New (you can set your defaults in your profile settings). All is a useful way to find stuff to subscribe to. When you search for and subscribe to a 'foreign' community, you're automatically adding it to the list for 'All' for all of Lemmy.zip
For mobile browsing, there are several apps with the "official" one being Jerboa (maintained by the Lemmy devs). There are also quite a few that are being developed right now such as Sync for Lemmy.
You can find a list here: https://kbin.social/m/kbinMeta/t/71764 as mentioned by Adanisi in a comment below.
And most importantly don't forget to enjoy yourself