Pop'n Music (ポップンミュージック), most commonly shortened to Pop'n, PM or PNM, is a music video game in Konami's Bemani series. The game is notable for its bright colors, upbeat songs, and cute character graphics. Although Pop'n Music was originally intended to be played by couples on dates, it has greatly escalated in difficulty since early iterations, and has since then attracted many players of Beatmania and other Bemani games.
Source: Wikipedia, "Pop'n music", available under the CC-BY-SA License.
The Arcade version contains all the music from Pop'n Music 1 as well as 2. The Console version is an 'append disc' which is essentially an expansion disc with more songs for Pop'n Music 2. This disc can also expand any other 'Key Disc' (or base disc) namely the later titles Pop'n Music 5 and 6.