You receive a virtual currency called Steem. Steem is traded on open markets, kind of like stocks, which gives it a "real-world value." One Steem is currently worth a little over $4 each. There are ways to cash it out into US dollars, British pounds, other government currencies, precious metals, or many other things.
You can check out this post for directions on how to turn it into government currency: https://steemit.com/howto/@ilyastarar/how-to-cash-out-steemit-rewards-as-real-money-steemit-withdrawal-guide
If you don't like that guide, there are many other guides on Steemit for cashing out your Steem.