You don't need to read the full 300-odd pages of the
biblatex documentation, the six pages 8 to 13 (§2.1 Entry Types>§2.1.1 Regular Types) should be enough for a first impression.
That section of the
biblatex manual lists all regular entry types and the fields each type supports. Most field names are self-explanatory, but you can look up the exact meanings of those fields in §2.2 Entry Fields>§2.2.2 Data Fields (pp. 16-25) and for more involved stuff §2.2.3 Special Fields, pp. 26-30. Section 2.3 Usage Notes has some useful hints about the subtleties of some fields.
biblatex-examples.bib, which you already mentioned is a very good resource to get to know the types and fields by example.
The Wikibook has a page about bibliography management (https://en.wikibooks.org/wiki/LaTeX/Bibliography_Management) and its
biblatex section has a large table listing many entry types and fields.
Some of the resources listed in biblatex in a nutshell (for beginners) also have primers or longer sections about the data model of
biblatex. Paul Stanley's
biblatex introduction discusses the most common types on pp. 22-30. Knut Hegna and Dag Langmyhr's
biblatex guide has two tables with common types and fields along with a short explanation. French speakers may want to consult chapter 10 of Maïeul Rouquette's (Xe)LaTeX Appliqué aux sciences humaines, pp. 79-91. Most introductions don't want to flood their readers with all types, because not all of them are as regularly used as the big five
All of this applies to the default data model as used by the standard
biblatex styles. The default data model is the base for the data model of most (all?) contributed
biblatex styles as well, but those may very well define additional entry types and fields or otherwise modify the default data model. In that case you will want to read the documentation of the contributed style as well.