Basically the thing that ruins lives. RuneScape is an MMORPG
made by Jagex
where you complete quests, play games, and level up your skills to a maximum level of 99. Many people say that RuneScape is nothing compared to WoW, but that's because RuneScape is free. Players can also subscribe to the premium parts of RuneScape, also known as the Member's Zone. The MZ is almost 3X as big as the free zone, has more skills, and more quests. I recommend playing it, but in little doses, because it can be highly addicting. If you want an MMO that you can play for free or pay just a little per month, this is a game that you would like, but you have to get play it for about a year or so to fully appreciate it.
RuneScape is a fun MMO, but it takes about a year to get used to.