Dwarfism, also known as skeletal dysplasia, is a medical condition where a person is of extremely small size. Dwarfism is also characterized by certain physical features, such as an unusual shaped face or skull. Persons with this condition also have disproportionate body measurements between the upper and lower half of the body or in the span of their arms. It's usually inherited due to a lack of bone or cartilage development. This is why people who are suspected of having the medical condition are referred to a genetics clinic for diagnosing it.
Trudi is different because she has dwarfism. What she discovers, however, is that everyone is different in some way. Some people are different physically, while others are different mentally where it doesn't show on the outside.