What does it mean when they put tubes in your ears?

It means that doctors take little tubes (literally, think like a little itty bitty straw no longer than a pen tip) and push them through the ear drum. It stays in the ear drum and creates an opening between the inner and outer ear that keeps fluid from building up behind the ear drum. It's kind of like putting a sewer pipe in a dam to let the water go to the other side of the river.