What to be told to my 7yrs old child whn he asks about whisper,condom advertisemants shown in t.v?

I would tell him that they are something men sometimes need to use when they are older because sometimes thier private part can get an infection and by wearing the condoms it protects them. You dont need to go into all the part and stuff . This way you are not lieing to him and your not really getting into all the fine details which he really doesnt need to know about yet. If you tell him in a way that seems like no big deal he will be satisfied with your answer. He probably already knows more or less what they are for from other kids and is just testing you or wanting to see how you will react. Just act like it is no big deal as if he were asking about a new type of shampoo or something. If you dont answer his question he will still be curious so you dont want to just try and change the subject.