What are the two major types of hearing loss?

Both types can occur in the same person.  Your outer ear gathers sound waves and funnels them down into the ear canal, striking the eardrum, causing it to vibrate.  Three tiny bones in the middle ear conduct the vibrations from the eardrum to the cochlea in the inner ear.  If anything interferes with the transfer of sound waves up to this point the type of hearing loss that may result is called conductive.  The sound vibrations having reached the inner ear create waves in the fluid inside the inner ear, stimulating thousands of delicate hair cells. This generates nerve impulses in the auditory nerve, which lies just beyond the cochlea, which are carried to the brain therefore, making sense of sound.  Anything that damages the hair cells or blocks the transmission of the nerve impulses can lead to sensorineural hearing loss. 

Conductive hearing loss may be temporary or permanent, can be caused caused by a buildup of earwax or an ear infection, or other middle ear conditions.  Sensorineural hearing loss, which is almost always permanent and far more common and be caused by aging, excessive and prolonged noise exposure, infections, hereditary factors as well as a host of other causes. Surgical procedures and medications can treat conductive hearing loss, but rarely sensorineural hearing loss.