Research into the treatment of burn injuries has advanced over the past several decades. Even if you have burns covering 90% of your body, you still have a fairly good chance of survival. However, it is unlikely that you will recover to your pre-injury condition. You will almost certainly experience scarring and other impairments that are typically permanent. 

The severity of a burn depends not only on how much bodily surface area it affects but how deeply the damage extends through the different layers of skin and tissue. According to the National Institutes of Health, there are up to six degrees of burn classification. However, like most people, you may only be familiar with the first three. 

Your skin consists of two layers: the dermis, which is the deeper layer, and the epidermis, which is the outer layer. A first-degree burn is the least severe and only affects the epidermis. It usually heals within a matter of days and causes no scarring. A second-degree burn extends through the epidermis to affect the dermis, where it can cause blistering and scarring. You may require a surgical skin graft to repair damage from a second-degree burn. 

A third-degree burn extends through both layers of skin to affect the tissues underneath. Structures in the skin that a third-degree burn can destroy include sweat glands and hair follicles. Third-degree burns require treatment in the form of skin grafting. 

Doctors may classify burns that extend down to the fat layer under the skin, the muscle or the bone as fourth-, fifth- and sixth-degree burns, respectively. However, some feel that the third-degree classification is sufficient to communicate the degree of severity.