What do achievements and extras do in Lost Via Domus

The basic achievments, meaning the achievement that have titles already, simply unlock gamer points that truly only apply to the XBOX 360 console's achievement tracking system. The special achievements, meaning the optional ones that you really actually have to discover on your own outside of the linear story line, will unlock some very pretty concept art for the game in the Extras section of the title menu. None of the art is revealing of anything that wasn't specifically in the game, so there's no inside info to be gained, just something nice to look at when you haven't completely fulfilled your Lost fix.