A grammar point that expresses that the action or situation in the second part of the sentence comes about after the action in the first part occurs. Thus it differs from ~고 whose use is not indicative of sequential order.
You typically can’t use movement verbs before this grammar point (e.g 가다, 일어나다, 내리다, 앉다 etc.), instead when you want to use such action verbs you should use the grammar point 어/아/여서 instead.
In addition you cannot use ~으세요, ~읍시다 or ~겠어요 and ~을 거예요 (if you want to talk about future events you can use ~을까 하다 or 기로 하다).