Many dogs will recover from IVDD without surgery, but currently there are no robust criteria to distinguish dogs that unequivocally require surgery from those which will recover whilst receiving conservative medical management.
Your vet might have explained your dog has IVDD and will likely need surgery. Surgery is not always possible for some dogs. Perhaps your dog is too old, an operation is too risky, or you would prefer a non-surgical route. Talk through the options with your vet as they might recommend surgery is the only reasonable route however, if you decide to avoid IVDD surgery, there are conservative management treatments you can try.