If something happens outdoors, it happens outside in the fresh air rather than in a building. It was warm enough to be outdoors all afternoon The ceremony was being held outdoors. indoors
You refer to the outdoors when talking about work or leisure activities which take place outside away from buildings. I'm a lover of the outdoors Life in the great outdoors isn't supposed to be luxurious. the (great) outdoors the countryside far away from buildings and cities
where the air is unconfined; "he wanted to get outdoors a little"; "the concert was held in the open air"; "camping in the open
The environment outside of enclosed structures; the natural environment in the open air
where the air is unconfined; "he wanted to get outdoors a little"; "the concert was held in the open air"; "camping in the open"