Page flipping
Changing which framebuffer the display reads from instead of copying the finished image — one pointer is swapped at the vertical blank.
With double buffering there are two image buffers: the screen reads one while the next frame is drawn into the other. Page flipping swaps them by rewriting the graphics hardware's base address, so the finished buffer becomes the visible one in a single instant. The alternative is to copy (blit) the whole image, which spends memory bandwidth every frame.
Flip mid-scan and you see half the old image and half the new — tearing. So the swap is traditionally synced to the vertical blanking interval (vsync). The trick was already standard on VGA cards (Mode X) in the early 1990s and survives as the foundation of every modern swap chain.