I think they are probably referring to outer ear infection (aka swimmers ear). It makes the ear painful, possibly itchy, temporary partial hearing loss, fever, discharge and inflammation.
I think as divers we are more vulnerable to this because our ears are made moist for long periods making it easier for bacterial/ fungal infections to get a grip. Simple things like drying your ears and wearing a hat after a dive can help reduce the possibility. You can get commercial products and there are other home remedies for getting trapped water out of you ear which will help too.
