what is a zip+4 code and how is it different from a 5-digit zip code

what is a zip+4 code and how is it different from a 5-digit zip code

what is a zip+4 code and how is it different from a 5-digit zip code. There are any references about what is a zip+4 code and how is it different from a 5-digit zip code in here. you can look below.