Factories and blueprints
Many things in the game are made up of two parts: a factory and a blueprint. This includes materials, entity templates and class wrappers. The thing these all have in common is that they are generally used as part of the entity system.
Below is the structure of an entity template.
You don't actually have to worry about this when editing entity templates; QuickEntity merges these two as well as making a lot of things much easier to work with.
As mentioned in Overview an entity template fundamentally is just a collection of other entities, whether those are UI controls (UICT/UICB), classes (CPPT/CBLU) or other entity templates (TEMP/TBLU).