SDK
Also known as: software development kit
An SDK is a library that wraps an API in the idioms of a particular programming language, so a developer calls a function instead of assembling an HTTP request by hand. It usually handles authentication, retries, pagination and error types.
A good SDK removes an entire class of integration bug, because everyone using it inherits the same handling of the awkward cases. It also gives the API owner one place to fix a problem for every customer on that language.
The trade-off is version drift. SDKs lag behind the API they wrap, and an unmaintained one becomes the reason an integration cannot use a feature that has existed for a year. Check when it was last released before depending on it.