Literally, outdoors is beyond the doors of your residential home. Figuratively speaking, the outdoors is the wilderness.
Being outdoors is an expression for being in the wilderness, or at absolute minimum, being outside the house in a natural environment .
A park is considered natural for these purposes.
Example: Danny and his friends search for gold in rivers in New York State. "Danny and the gang say they're not disappointed if they don't find gold -- they just love being outdoors."