Original: Upon its official release, RuneScape 2 was renamed simply RuneScape, while the older version of the game was kept online under the name RuneScape Classic.
Simplified: The game first started in 2001 as Runescape (now referred to as RuneScape Classic), but the code and graphics engine was rewritten in 2004 to form Runescape 2, the game that is playable today.