The 'bt' in the site's name refers to BitTorrent, which is a P2P ("peer to peer") file distribution system roughly similar to (but, in many people's opinion, somewhat better than) Gnutella. [You might not have heard of Gnutella but you've probably heard of the most popular program which uses that system, Limewire].
BtScene.com doesn't actually host any files. It simply provides an 'indexing system' so that users of programs (such as uTorrent) which use the BitTorrent system can find what they're looking for on other users' PCs.
Just as with using Limewire, DOWNLOADING copyright material (without the consent of the copyright holder) is illegal. But unless it's done for commercial gain (or on such a large scale that it's to the serious detriment of a copyright holder) it's only a CIVIL offence (for which you can be sued but not fined or sent to prison). However, like all P2P systems, BitTorrent requires you to make the files which you're downloading available to other users of the system. That counts as UPLOADING, (= 'distribution' in the eyes of the law), which is a CRIMINAL offences as well as a civil one.
Chris