A typeglob is a slot in a symbol table. Essentially, every symbol table is a hash with keys being the names of globs and the values being the typeglobs (the terms "glob" and "typeglob" are frequently used interchangeably). Each typeglob has a variety of "slots" which correspond to each data type that Perl allows (scalars, arrays, hashes, filehandles, etc.) In the case of the typeglobs you listed, they are probably filehandles, though there is nothing to prevent someone from using %STDIN as a variable name which, if a package variable, could be accessed via the *STDIN typeglob.

I realize this probably did not answer your question, but that's because there's a lot to talk about for this particular topic. I would suggest consulting perldata and perlmod for an introduction to typeglobs and symbol tables.