It is important to define conditions correctly and accurately as on a practical and financial level they can be used to correctly assess the amount of assistance a individual receives from the state.
When trying to answer this question you must try to not confuse genuine disability and a congenital condition with long term ill health. In many cases someone who has a health problem (even a long term one) may find that their condition improves with time and treatment. This is not the case with disabled people who have a handicap that has a substantial effect on their ability to lead a independent life.
Some people are born disabled and others become disabled through accidents. For example someone injured in a car accident may have limited mobility and may have to use a wheelchair or other disabled aids to move around. In this example the person will be classified as disabled.
You should also note that certain disabilities are hidden on the outside any may not be visible to other people. Certain people may not want to disclose that they are disabled if it is not physically obvious. This is especially true it there are no benefits for them in doing this or they may have other reasons.
Types of various disabilities:
Hearing and being deaf
Mobility and motor impairments
Mental health problems