Welcome to Steemit maryna91. The official FAQ can be found here and has A LOT of information https://steemit.com/faq.html - Also remember, Steemit is just ONE of the sites built that uses Steem the blockchain. You should also check out DTube and DSound for starters and if you're a gamer, Steem Monsters! There are many other cool apps but I can't list them all here, there's just too many! But I'd also like to mention Steempeak, it's a better blogging platform that has a lot of cool features. Welcome to the blockchain! :) Oh, and if you're interested in creating your own tokens or smart contracts, check Steem engine!