-고 links two actions with no connection beyond order: 청소하고 쉬어요. -아서 or -어서 links them causally, or means the first has to happen before the second makes sense: 집에 가서 쉬어요, meaning I go home and rest there.
Examples
- 청소하고 빨래를 해요.
- I clean and then do the laundry.
- 집에 가서 쉬어요.
- I go home and rest there.
- 설거지를 하고 텔레비전을 봐요.
- I wash the dishes and watch television.
The mistake to avoid
-아서 cannot be used with a past ending on the first verb: 갔어서 is wrong.
Where this fits in
하루 일과, Korean A2: Talk about your daily routine, habits, and how often you do things.