Is karma essential for posting?

So I wanted to make a post on some subreddit but it said "too low karma to post". My question is, do we need certain karma points to post in those big subreddit pages? Ig yes, then how much?

Also, I posted something on another subreddit but it said "since you have low karma it needs to be approved by a mod" and then it never got approved by anyone even after a week. Does every post in such subreddits need to be approved or only low karma accounts like me? :-(