OpenGL is a crossplatform library which handles 2D/3D graphics. The OpenGL rendering pipeline can be accelerated by hardware allowing real time rendering of complex 3D scenes (lots of geometric details, textures, particles, lighting, blending, ...).

TA3D uses OpenGL to render everything from its GUI to the game itself. OpenGL comes with an extension system which allows adding functions and effects that were not planned in older versions (read as soon as you hardware and driver support a feature you can use it :P). TA3D can use several extensions for multitexturing, shadowing, GLSL fragment and vertex programs, ...

see  http://www.opengl.org for more information