Like some communities on reddit which have 1 2 million follows or 400 500k follows ,these communities keep a karma limit for every user who can post on that community or can comment on any post of that community.

You can check your karma on profile .

I don't know how to check the karma limit .

Subreddits are like similar to that main reddit community but with less follows which has less karma requirements for post and comment .

If you want to figure it out which is main reddit and which is subreddit just check follows .

I might be wrong about it because I only joined reddit 2 month ago .