Medically it is referred to as cerumen and consists of dead skin, hair and water-soluble secretions from the outer ear canal.
It serves several functions – one of which is an an antibacterial, self-cleaning lubricant. Excess cerumen usually funds its way out of the war canal through the washing of hair and jaw movement.
Occasionally it can collect and become compacted, which can lead to tinnitus and slight hearing loss. Find out more about tinnitus here.