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Curators find and submit undiscovered posts by new authors, reviewers approve (or not) them and upvote with the @curie account. @curie's voting trail follows, rewarding the post. Curators and reviewers are paid for their services. That would be a simple way to put it :)

Curators are a team or practically anyone ? Also i heard they only support new authors with reputations less then 48, is it true ?

Anyone can be a curator. Good curators receive greater submission limits, bad curators receive none, etc. Yes, that's true, currently only authors under Rep 52 are eligible for submission.

Thank you for the answers, how do you submit posts ? and can you submit yourself ?

Find #curie on Steemit.chat. You'll find all information there :)

And no, you can't submit yourself.