Guild Wars 2

Hi. I’ve read about it in the wiki but I still can’t understand what it is. Can someone explain it to me?

mini dungeon which get harder by each level. Mists is an afterlife world in Tyria, but asuras could hack into it and now have acess to it. Mists takes resemblence of times and world around it. So fractals are different fragments of the world from different times, on each odd level you have 3 mini dungeons on even levels 4 where 4th is always the same. it gets harder and after lvl 10 you need ascended gear to infuse agony resistance to resist tons of damage