Mariana's explanation and examples are correct, but it's not the whole story: The key point to understanding the present perfect (both simple and continuous) is that the action has an effect on the present situation. The continuous aspect indicates a repeated or continuous action, but it does NOT always indicate an action that is still happening. For example, taking Mariana's example: You (person B) arrive home from the tennis club, and you go straight into the kitchen to get a drink of water. You meet a family member (A) in the kitchen: A: You look tired. B: I am tired! I've been playing tennis for an hour. In this case, it is obvious that you're not playing tennis at the moment. But you use the present perfect continuous to relate the action of playing tennis to the present moment - it is the reason why you are tired.

O Present Perfect Continuous é usado, basicamente, para enfatizar a continuidade de uma ação que começou no passado e que se prolonga até o presente. I've been playing tennis for one hour. (Estou jogando tênis há uma hora.) Women have been fighting for their rights during the last decades. (As mulheres têm lutado pelos seus direitos durante as últimas décadas.)