If your program is to be used by other programs or is a 'control' it will declare the functions that it provides in the PE header of the component DLL, OCX or whatever. This is the mirror image of an 'import' function. The loader has to match the exports with the imports required when it loads a program.
InspectExe lets you list all the exported functions in a .DLL or .EXE file.
It will also show you the functions exported by a static library .lib file :