One of the under-the-hood features in Android 7.0 Nougat is native Support for the Vulkan API. The Vulkan API is the successor of now old OpenGL API and has developed by the khronos group. When the first developer preview was announced back in march, Google promised that it will add support for the Vulkan API in an upcoming preview and as a result, it was implemented by Google in the Android N developer preview 2. Vulkan is a cross-platform open source graphics API that provides tools for developers to implement this API in their gaming apps to get benefits of power efficiency and lower GPU overheads.
Google has implemented the Vulkan API on their compatible Nexus devices since the 2nd Developer preview - such as the Nexus 5X, Nexus 6P, as well as the Nexus Player. Now it turns out that the Nexus 9 tablet will not get support for the Vulkan API. As in recent Reddit AMA held after Android Nougat's final preview release, Google's engineering team clarified that the Nexus 9 will not get Vulkan drivers, hence making it unsupported for Vulkan. The HTC-made Nexus 9 tablet was launched back in October of 2014 with Android 5.0 lollipop and runs on NVIDIA's Dual core Tegra K1 chipset. Google didn't give any reason or detail for why the Nexus 9 is not getting Vulkan support, but, it's believed that hardware compatibility is the reason behind it, as only devices running Qualcomm snapdragon chipsets have received Vulkan API support so far. Aside from the Nexus 9, the Nexus 6 is also left out of the list of supported devices.
Unlike previous graphic APIs, the Vulkan API allows multi-thread utilization that makes it possible to utilize multiple cores to achieve great performance without stressing much on the CPU; another notable feature of this API is that it gives the developer more access to GPU so that developer can extract more performance from the graphic processor. Implementation of the Vulkan on Android will greatly improve the gaming performance on the platform. That means you will be able to play your favorite games without worrying about battery draining as quickly and with much less performance hiccups. It's also worth noting that implementing this API wouldn't improve performance in apps itself, rather it's up to developer to utilize the API in the app. Google, Samsung, Huawei, Sony, Qualcomm and several other big names are listed as members and working on the implementation of he Vulkan API on their products.