Total & Permanent Disability cover pays a lump sum if you suffer a permanent disability (according to the policy definitions) that prevents you from working. Payments are generally not made until the disability has been evident for a period of 6 months, and until the insurer deems that you are unlikely to work again.
TPD benefits are often used to eliminate debt, pay for medical expenses or fund and permanent changes to your lifestyle that are necessary as a result of your disability.