Google Maps API are that maps that have additional content for own webpages and it allows the embedding of Google Maps onto pages of outside developers. API (Application Programming Interface) means a set of subroutine definitions, protocols and tools for building application software. A good API makes it easier to develop a computer program by providing all the building blocks, which then are put together by a programmer. And the SDK (Software Development Kit) gathers a group of tools that allows the programming of mobil applications.
We can find that exist different kind of APIs and SDK, as for example:
In your business with this maps you can build customized, agil experiences that bring the real world to your users with static and dynamic maps, Street View imagery and 360º views. As we can see it in the maps applications as Google maps, Maps.Me (an open street map), TomTom (apple maps) and here map (nokia).