Windows 7 includes DirectX 11, and Windows 10 includes DirectX 12.
Other non-game applications may use DirectX for features like 3D graphics. If they don’t, they use the cross-platform OpenGL or Vulkan APIs instead. Many games on Windows use DirectX’s Direct3D for graphics. It’s a group of APIs (application programming interfaces) developers can use for 3D graphics, video, multimedia, sound, and gamepad features on Windows.