Old School RuneScape (OSRS) is a variant of the popular game based on the source code from 2007. OSRS was introduced in 2013 as an alternative to the then-current edition of the game. Most of the content and features that appear in the game is decided upon by the community through a series of polls.
RuneScape has been around for a very long time. The game was first released in 2001 and has evolved a lot over the past 18 years. OSRS allows players to play in a much more classic look and feel.
If you want a taste of what Runescape looked like more than 10 years ago, give Old School a try.
More Old School Runescape resources:
Old School Runescape Wiki – everything you need to know about the game
OSBuddy – a vital companion tool for Old School players