Yeah, that's more-or-less correct. SDK, Software Development Kit, is a package that a company releases to help you write programs that use their product. For example, the Java SDK includes the compiler and everything else you need to create Java programs. Likewise, the Nvidia SDK includes everything you need to take advantage of their video cards and the DirectX SDK includes everything you need to use DirectX in your program. SDKs often include headers and libraries that you include in your own program to interface with the company's product. For example, the DirectX SDK includes the header files dinput.h, etc as well as the libraries dinput.lib, etc. Often, but not always, the SDK includes examples and tutorials as well.