Taps are somewhat similar in appearance to drill borers. They have special threading lines along the length of the rod that are needed to create female couplings (nuts). The tap is placed against a prepared metal and then driven through to essentially create a thread. Tapping may require manual power (and a wrench), or additional power tools, (e.g. drills).
Dies are utilized to form male couplings (bolts). They have thread patterns cut out inside of a circular metallic disk, which is rotated around the metal rod (this process also may require a wrench) to create a bolt.