When I watch the food channel I smell the food cooking?

Sometimes when I watch tv like the food network and they're cooking sometimes I get a whiff of the food. Once I was watching Rachel ray's show and she was cooking something and said "I wish there was smell-o-vision" and I suddenly got a whiff of the food she was cooking. Why does this happen to me? Also if I think about about something I smell it like it's there with me. Why does this happen?