Actually the non-term "progressive streaming" is misleading here. Progressive Download is where a file transfer is initiated, and during the transfer the client is able to play the media given the media and the client support that function. The server just has to transfer fast enough to allow real-time playback, so no exceptional configuration is necessary.
Streaming is different, usually the server software must specifically adjust the rate of transfer, possibly accounting for limited bandwidth. In addition their usually isn't file used on the client to store data received.