The AdWords Application Programming Interface (API) allows developers to use applications that:

The AdWords Application Programming Interface (API) allows developers to use applications that:

  • Interact directly with the AdWords server.
  • Can appear throughout the Google Search Network.
  • Are accessible only through AdWords Editor.
  • Can be uploaded into the display ad builder.

The correct answer is:

  • Interact directly with the AdWords server.

Explanation: The Google AdWords API lets developers build applications that interact directly with the Google AdWords server.

You can read more here: https://support.google.com/adwords/answer/2375503?hl=en