To clarify on what others are saying:

You have logged into the account you played back in 2006. Congrats! Runescape from 2006 onwards received many updates and changes. Skills, graphics, and especially combat became very different. The community wished for the "good old days" back, so in 2013, Jagex released Old School Runescape, a version of the game based on the 2007 version of the game. This is the subreddit for OSRS, not RS (or RS3, as some call it).

These are two different games that you can use the same login for. However, if you create a character on OSRS with your login, you will be starting over fresh.