Poker freerolls are the superior place to learn poker as they have the benefits of learning at a real online poker room without the risk.
For this reason they are often a great starting point for people who are looking to play real money games but are just starting out playing poker.
They do, however, offer real cash prizes so they can be a great way to increase your winnings without adding any extra risk. A Poker Freeroll is just like any other real money poker tournament except they are completely free to enter.