Essentially, lemmy.world is an email provider right? Like Gmail.
And communities [or subs!] are forums. While these forum posts are made by people who are on the lemmy.world instance, every other provider [instance] can see them, provided the instance owner has not decided to block other providers [defederated].
As long as you are browsing ALL instead of Local [local only shows subs on your own instance], it’s effectively reddit.
It may be worthwhile to make an account on an instance which features your country for Lemmy performance purposes, plus the local communities [subs, remember] may be very relevant for you, albeit probably very small in terms of users.
Signing up for lemmy.world is like signing up for shit, monopolised, slow internet in America? It has lots of customers, but that new upstart fibre company [small, fast instance] will let you see the same pages as shitty, slow Comcast.
(I’m not knocking Lemmy.world, just using it for this analogy)
That’s what I make of the fed so far, pretty cool.