If you are convicted of a fourth DUI, your license is revoked instead of suspended.  A drivers’ license suspension is for a fixed period of time and at the end of that period you can get a license if you can show SR-22 insurance.   A revocation is for an indefinite period of time though this does not usually mean forever.  To get your license back you have to apply to the DMV at the end of the revocation and they have to reestablish your driving privilege.