The term "ear infection" refers to an inflammation or swelling of the middle ear, which is located directly behind the eardrum. This area contains the Eustachian tube, which connects the middle ear to the back of the throat and helps equalize air pressure on both sides of the eardrum. When fluid builds up in this area due to a viral or bacterial infection, it can cause pain, redness, and swelling. This condition is commonly known as otitis media.