Information visualization - Help needed

I was using Azureus lately to download a Bittorrent file. After some months of inactivity it updated itself a dialog praised recent changes like enhanced statistics, more information, and such.

But one of the enhanced information panels really confuses me. Can anyone please help me to understand the information presented in the image below?

I guess the numbers stands for the number of reachable sources for that piece. But what does the line type stand for (we have solid, dashed and empty lines here)? Gosh, how many dimensions are packed in this diagram? What exactly should red and blue triangles with varying sizes tell me?

confusing Azureus statistics

Btw. I'm using Transmission most of the times...