So #1 is more like he is wearing a mask RIGHT NOW. I can see that he is wearing a mask, or I know he is wearing a mask. Example: You see your dad leave the house with a mask on but your mom did not. Your mom: Did he leave the house without a mask? You: He is wearing a mask. And #3 is more of a hypothetical or situational answer. In which, even if you don't know if he is wearing a mask right now you know that he wears a mask to cover his face when he goes outside. Example: Your friend ask what your dad does to protect himself when he goes outside. Friend: Does your dad put anything on his face when he is outside? You: He wears a mask. (see this time, you don't know if your dad is wearing a mask right now but you know he normally wears a mask when he goes outside so you say he does.)