If you cant afford one, one will be appointed to you?

Public defenders are paid for by taxes. Before public defenders existed, courts often ordered lawyers to appoint certain defendants for free, which as you can imagine did not exactly make the lawyer eager to defend his client if it would drag on the case. Various places established public defender's offices (the first being Los Angeles), and in 1963 the Supreme Court established that indigent defendants have a right to a lawyer free-of-charge in all state courts (Gideon v. Wainwright).

Of course public defenders care about winning. It is impossible to defend someone without caring about their case; many public defenders get quite emotionally invested in their cases. Public defenders are able to deal with the stress this brings because they're there because they want to be--private practice is often easier and pays better. It is also to the public defender's benefit if they win, of course; a good case record may boost the attorney's career prospects.

I believe that the state pays for the Public Defender. I had a class with a Professor who was a Public Defender and he stated that they do a good job. There are also there to represent you since you ( as a lay person) do not know the law.

Public defenders are paid for by the Tax Payers.