Every time I look in the monitor window and click on the "show" check box under incoming searches, a message appears saying that my client is a leaf node shielded by an Ultrapeer so I only see few or no searches. That is true. Before, I used to have a lot of people downloading from my PC. Now, no one is downloading from my PC and barely anyone is searching.

What is a leaf node and what is an ultrapeer? Also, what does the message stated above mean?