Typed specifies the type of function arguments:

FunctionCompile uses Typed annotations for compiling code:

The CompiledCodeFunction evaluates with an argument that matches the type:

If the type of an argument does not match the declared type, an error results:

is a compound type that takes another type as its argument:

The resulting compiled function has the type:

The computation then proceeds as expected:

A function type can be supplied as an argument to a compiled function:

The computation then proceeds as expected:

Typed can also be used within FunctionDeclaration:

The declaration is then supplied to FunctionCompile:

The compilation incorporates the declared function as expected:

When used in the parameter list of a pure function, Typed is effectively ignored in non-compiled evaluation:

When used in the body of a pure function, Typed remains literal under ordinary Wolfram Language evaluation:

Typed is inert under ordinary evaluation:

TypeHint, which can also be used in functions, evaluates to its first argument during normal evaluation: