How does tinnitus occur and what could be done to lessen the symptoms and end it altogether?

No short answer. An explanation of the cause of tinnitus is long and drawn and outside the parameters of this space. Basically tinnitus is a flow noise or an electrical noise in or around the ear that has been "unmasked." unfortunately there is nothing currently available to "end it altogether." there are an assortment of natural, alerternative and medical remedies that could bring some relief.
Tinnitus. The most common cause of tinnitus is hearing loss. No medicines have been shown to help, but the severity can be lessened with masking the noise (background noise), using a hearing aid (if indicated) and trying biofeedback. Tinnitus can also be from medicines, stress, rarely rumors or irregular blood flow in the head.