there are four leauges. Hard core, soft core (default), anarchy and onslaught. Onslaught is a hard core version of hard core, if you die here or in HC you go to SC. Anarchy is like a d2 ladder version of sc with a few things that can only accur in anarcy. in 4 months this leauge rests and all chars go to sc.

Everyone ends up in softcore eventually.

In anarchy league you can sometimes randomly encounter NPC controlled characters that use skills.
When you kill one, they drop a magic+ item from each equip slot.

its like diablo 2 ladder and non ladder

can i meet them on lower levels like 1- 20? i like just remaking my characters looking for more and more better gear for low levelers

Worthless to do that, they are randomly spawned and don't spawn that often. Their drops are also not that great. You have better luck finding gear doing ledge runs or whatever runs you can do easy at the time.