Short answer: a typeglob is a symbol table entry; if you have (non-lexical) $foo, %foo, @foo, &foo, and format foo, they are all contained in the same typeglob *foo (along with a file/dir handle). Because filehandles have no specific sigil, you can only mention them in perl by way of the glob.
in reply to What are typeglobs (useful for)?
So there are two cases where you'd use a typeglob: as a filehandle, or to muck about with the symbol table.
The most common case of the former is to use one of the
perl provided filehandles *STDIN, *STDOUT, *STDERR, *DATA. (The * is unneeded if passing to a function or builtin having a * in the prototype.) For non-perl provided filehandles, using the newer lexical filehandles (actually just a reference to a typeglob, stored in a regular scalar variable) obviates the need for a typeglob.