It's a copy of RuneScape each private server differs on how it works though, like in some you can spawn anything you want.
Watch out for virus' too a lot of them are.

A RSPS is a Runecape private server. Illegal sites that are made off of jagex's game runescape. They are easier to level up on than real runescape, but if you get caught running one by jagex, you can get done for copyright.

iClanx wrote A RSPS is a Runecape private server. Illegal sites that are made off of jagex's game runescape. They are easier to level up on than real runescape, but if you get caught running one by jagex, you can get done for copyright.

wrong it is not illegal, they are legal as long as they are purely for learning the language of java, and taking no donations, or any form of money, if you break one of those rules jagex could sue u, but they most likely will not unless you are significantly harming the runescape population and economy

It's the exact same thing of runescape but private servers are always free unless you want "special items" the game is way easier than Runescape and there are a lot of servers that you can play on. But they don't have that much players. IMO stay with Runescape.