Literally, couple means two. But the phrase can be used as an idiom at times which usually means a few days, ranging from 2 to 5 days. The speaker is not so precise as to how many days it will be, but is sure that it falls between the range of days given.

I rarely hear it being used to mean specifically 2 days. Most people mean "a few days" when they say "a couple of days"

It means it is not one day - so any number of days other than one

do you mean "a couple of days"? i think it means several days, it's possible to say it two days too.