In a dynamic linking system you can build dynamic modules that are loaded and relocated by a dynamic loader at run time. The dynamic loader can also perform dynamic symbol resolution: resolve references from dynamic modules with the definitions from other dynamic objects.
Only symbols explicitly imported or exported have dynamic linkage and participate in dynamic linking. Normal global symbols don't participate in dynamic symbol resolution. A symbol is exported if it is visible from a module during dynamic symbol resolution. A dynamic object is a dynamic library or a dynamic executable. Such a dynamic object imports a symbol when its symbol references are resolved by definitions from another dynamic object. The dynamic object that has the definition and makes it visible is said to export the symbol.