Essentially, an album can be any collection of media like photos, music, video and the like. When it comes to music, an album is a collection of audio data, put together by one artist or band, to distribute all audio files together.
The first music albums date back into the early 20th century, where they were sold as vinyl records or LPs. Alongside with the vinyl, albums were released on audio cassette, until both were more or less replaced by the CD format. Albums pressed on CD usually contain music in the MP3 format.