Entities are just like autotext entries or shortcuts. With an entity, you define its name and the text it should expand into when referenced in your document. Then, when you type the entity reference in an XML document or DTD, it is replaced with text you defined.
There are several types of entities, but they all work in the same way, and they are all defined through a DTD. The differences lie in where the entity can be expanded, and what kind of data it contains.
Entities can be divided into two main types: general entities and parameter entities. General entities can be expanded only in XML documents; parameter entities can be expanded only in DTDs.
General entities can be further subdivided into internal ...