Triple Buffer

i wanta know what is triple buffer ? what is its advantage? and how implement in opengl?

It means you have two back buffers and can always continue drawing the next frame even while your waiting on the next vertical blank which normally limits your maximum framerate to the monitor refresh.
The last back buffer which has been completed will be shown if the SwapBuffers finally occurs. Intermediate frames are thrown away. Imagine 180 fps with vsync on 60 Hz: Only a third of the drawn frames is really shown. Do something better with that time.

OpenGL supports only double buffering natively!

If an OpenGL driver would support triple buffering it would be done behind your back.