Steemit does not give money for posting if by money you mean US dollars, Euros or any other "regular currency". Steemit.com is just a website that connects the users to the Steem blockchain. The steem blockchain is a network of nodes that is not owned by anyone.

The code in the blockchain generates new Steem every day and this is distributed by the votes. The Steem tokens only have value if people use them or trade them.

Think of Steem as a foreign currency. For example if I try to buy things with pesos in Russia no one will accept them. Pesos do not have any value in Russia...but if someone is willing to trade them for Rubles and/or accepts them as payment then my pesos have value.