Mesa
Mesa, also called Mesa3D and The Mesa 3D Graphics Library, is an open source software implementation of OpenGL, Vulkan, and other graphics API specifications. Mesa translates these specifications to vendor-specific graphics hardware drivers.
Its most important users are two graphics drivers mostly developed and funded by Intel and AMD for their respective hardware (AMD promotes their Mesa drivers Radeon and RadeonSI over the deprecated AMD Catalyst, and Intel has only supported the Mesa driver). Proprietary graphics drivers (e.g. Nvidia GeForce driver and Catalyst) replace all of Mesa, providing their own implementation of a graphics API. An open-source effort to write a Mesa Nvidia driver called Nouveau is mostly developed by the community.
Besides 3D applications such as games, modern display servers (X.org's Glamor or Wayland's Weston) use OpenGL/EGL; therefore all graphics typically go through Mesa.
Mesa is hosted by freedesktop.org and was initiated in August 1993 by Brian Paul, who is still active in the project. Mesa was subsequently widely adopted, and now contains numerous contributions from various individuals and corporations worldwide, including from the graphics hardware manufacturers of the Khronos Group that administer the OpenGL specification. For Linux, development has also been partially driven by crowdfunding.
Introduction
The Mesa project began as an open-source implementation of the OpenGL specification - a system for rendering interactive 3D graphics.
Over the years the project has grown to implement more graphics APIs, including OpenGL ES (versions 1, 2, 3), OpenCL, OpenMAX, VDPAU, VA API, XvMC and Vulkan.
A variety of device drivers allows the Mesa libraries to be used in many different environments ranging from software emulation to complete hardware acceleration for modern GPUs.
Mesa ties into several other open-source projects: the Direct Rendering Infrastructure and X.org to provide OpenGL support on Linux, FreeBSD and other operating systems.