This might answer your question. Basically it is HTML encoding for a few predefined characters.
Characters like > and & are HTML Entities specifically, they are Named HTML Entities
It is not an encoding at all. Even informally, it is more often called “escape notation” or something like that, not an encoding.
Since the question seems to be just about the name of the construct, here are the correct terms:
In SGML, which is what HTML is formally based on up to HTML 4.01, the term is “entity reference”. It so happens that all entities predefined in HTML expand each to a single character, and this is why they are often called “character references” or something like that, but that’s informal. Even HTML 4.01 calls them “character references”, but normatively HTML 4.01 cites SGML, so that’s to be regarded as informal. In SGML, only notations that refer to characters by their code numbers, such as >, are called character references.
In XML, which is what XHTML is based on, the term is “entity reference”, too.
In HTML5, the term is “named character reference”.