Khronos, the consortium behind OpenGL and other open-source APIs, has released version 1.0 of Vulkan, the successor to OpenGL and OpenGL ES and AMD's Mantle initiative.
According to Anandtech, this is the first "hard launch" in Khronos history, as today also sees the launch of documents, drivers, SDKs, conformance tests, and beta support in addition to the specification itself.
Khronos' aim with Vulkan is implementing a low-level API that is simpler and more efficient than its predecessor. The company says that "simple drivers allow for low-overhead efficiency and cross vendor consistency," and that there is "layered architecture so validation and debug layers can be loaded only when needed." Another benefit over OpenGL is Vulkan's ability for multiple threads / cores to handle graphics work.
Vulkan is designed to work on most hardware that currently supports OpenGL, and will be available on Linux and Windows (including Windows 7, 8 and XP since it is not tied to the Windows driver model in the way that DirectX 12 is). Khronos says that there will be one unified framework for desktop, mobile, console, and embedded systems, so there won't be specific versions for each type of hardware.
Anandtech says that the Vulkan conformance test is already complete, and that 30 drivers have passed testing. Some of these will be released today for developers to use from the get go. Nvidia has passed conformance testing, and AMD has also said that it will be soon releasing a beta version of a Vulkan-enabled Radeon Software driver.
As for hardware, AMD has already committed to supporting Vulkan on its "Graphics Core Next" series, Nvidia has confirmed that it will support it from Kepler onwards, and Intel has confirmed support on Skylake, but hasn't given any word on Haswell or Broadwell yet.
With today's Vulkan drivers we'll also be seeing versions of games released with Vulkan support, the first one being Croteam's The Talos Principle.
If you're a developer, then you'll be able to start using the tools from today and start programming according to Vulkan's specification. LunarG is releasing its Vulkan source development kit today, which includes tools for development and debugging. Anandtech says that Khronos has released documentation, references, and source code for its validation tools, and loader tools for debugging.
What does this mean for gamers? Not too much just yet, but DirectX 12 and Vulkan competing will hopefully spur performance advancements over the next couple years.