Rendering API
A rendering or graphics API is used to achieve hardware-accelerated (i.e. running on a GPU) 2D or 3D rendering - as opposed to software rendering that runs on the CPU. The term can describe APIs that directly interface with the GPU through an OS-dependent driver implementation or an application-specific API that abstracts away the interfacing with the underlying rendering backend.
List of common rendering APIs:
Renderer API
A renderer or rendering API may also refer to a layer of a graphical application that serves to abstract away platform-specific concepts and functions. E.g., the same renderer API may be implemented using DirectX on Windows and OpenGL on Linux.