Doubt about sitting up

I see a lot of mamas here say that their LO's are sitting up without support. I'm confused as to what exactly that means. Does that mean that their LO can, from a lying down postion, pull herself/himself up to a sitting postion by themselves

OR does that mean that when YOU put them in a sitting pose they can stay there without falling (and not necessarily get to that pose by themselves???)

Please clarify.