There are number of different types of disability insurance policies.

Most of the variation is due to the amount of coverage provided. One type of disability insurance is described as "own occupation". Quite simply this means that if you are unable to perform within your own occupation then you get complete disability. Even if you take up another position that makes as much or more money, you still receive full benefits. This type of disability policy is very expensive. The income replacement policy only replaces the income that is lost. For instance, a surgeon who can no longer operate yet can teach, will have the difference between his teaching salary and surgical income replaced. And there are step rated policies. This type of policy increases in cost as you age and the chances of disability increase. This information is general in nature and should not substitute for the advice of an expert in the field.