File sharing is where you allow others to take files from your computer and they, similarly, allow you to take files from their computer. Any type of file can be exchanged.
Certain programs make this process simple and efficient. Napster was one of the earliest file-sharing software providers but after a court case they were shut down for copyright violation. Things have moved on appreciably since then. It was possible to shut Napster down because they managed all the file sharing from a single central server. Switching this server off caused the whole system to fail. File sharing systems nowadays are not centralised, and therefore can not be shutdown in this way. Additionally files are not downloaded from individual machines on a one-to-one basis. Sophisticated software such as Bittorrent will retrieve tiny pieces of the file from many machines simultaneously and then assemble them on your machine.
File sharing has it's legitimate uses. Collaborative working - where people around the world work together on a project. They will need to shift large amounts of data between themselves in a secure and efficient manner and these tools are perfect for the job.
If you want to know more about how this works CompuGuide will be pleased to assist.