Cassette systems enclose tape in a plastic housing which protects the media from contamination by dust and damage due to mishandling. 
Several formats exist for audio cassette recording and playback. 
The most common is the audio cassette designed by Philips in the '60s for consumer use.  With the advent of video technology digital audio tape recorders have been developed which make use of the same kind of cassette housings and tape transports. 

Systems which use video-type cassettes offer even greater protection from dust and fingerprints by use of a hinged door which remains closed while the tape is out of the recorder. 

The drawbacks of cassette systems are difficulties in editing and assembling selections.