SirHub is a pee-files sharing hub (=server) for the DC++ Network.
DC++ allows users to share files and chat over the Internet with other users.
Here is a short overview of what you are doing if you use DC++:
You download and run a DC++ client software. You connect with this software to a Server (=SirHub). In this software you select a folder on your computer. This is your share. The content of this folder is downloadable for other users that are also connected to the same Server (=SirHub). No one can see anything else of your computer.
So you can see and download the share of other users of SirHub, and the other users can see and download your share (=content of the selected folder).