The latest in the series, OpenGL ES 3.2 added additional functionality based on the Android Extension Pack for OpenGL ES 3.1, which brought the mobile API's functionality significantly closer to it's desktop counterpart - OpenGL.
Despite being only a bump in the minor revision of the API, OpenGL ES 3.1 was an enormous milestone for the API, as it added the ability to do general purpose compute in the API, bringing compute to mobile graphics.
OpenGL ES 3.0 was another evolutionary step for OpenGL ES, notably including multiple render targets, additional texturing capabilities, uniform buffers, instancing and transform feedback.
OpenGL ES 2.0 was the first portable mobile graphics API to expose programmable shaders in the then latest generation of graphics hardware. It remains a prevalent API today, and still is the most widely available 3D graphics API, and remains a solid choice to target the widest range of devices in the market.
OpenGL ES 1.0 and 1.1 were the first portable mobile graphics APIs, defined relative to the OpenGL 1.5 specification, providing fixed function graphics acceleration
Full OpenGL ES specifications, headers, and reference pages for all versions of the API can be found in the OpenGL ES Registry: