Long Term Disability policies have different definitions of what it means to be disabled. The test for the first two years is usually whether you can perform your "own occupation", meaning the essential tasks of your job before you became disabled. Beyond two years, this usually changes to the more difficult "any occupation" test, meaning you must be disabled from any occupation for which you are reasonably suited having regard to your education, training, and experience to continue to receive benefits.
These definitions are NOT as difficult to meet as they sound. Insurers often unfairly apply the these terms to justify denial. A Long Term Disability lawyer will find weaknesses in the insurer's position, obtain additional records, and retain experts to prove you meet both the own occupation and any occupation tests of disability.