You interact with an OpenStack cloud using a number of tools. The tool you choose depends on your use case in the cloud. Here are some starting points.
A Software Development Kit (SDK) is a collection of code, examples, and documentation that helps you to create applications in the language of your choice on OpenStack clouds. If your language or use case isn't covered by one of the official SDKs below, you may need to use the API or one of the other Known SDKs.
An OpenStack Command Line Interface (CLI) is a text based client that helps you to create scripts for interacting with OpenStack clouds.
An Application Programming Interface (API) offers a way to use the capabilities of a service by using predefined functions. Use the API when the programming language you're using is not supported in an SDK. Please consider contributing that work to one of the Known SDKs.