zip codes and their postal code equivalents are "real life" features that have very very strongly different definitons and use depending on the country you are referring to. In some places it isn't possible to talk about a zip code boundary in any reasonable fashion. One of those places is the US (which you are likely askinbg asking about).
Now you can build polygons from address information (using for example OSM and other sources) indicating roughly where the areas are, but we do not have such information directly in OSM.
Further reading: https://en.wikipedia.org/wiki/ZIP_code