Complex sentence: A variety of other actions may be taken on the previous screenbuffer and other backbuffers (if they exist); it may be erased from memory, or returned to the back of the swap chain for further processing.
Split into simpler sentences: A variety of other actions may be taken on the previous screenbuffer and other backbuffers (if they exist). The screenbuffer may be simply overwritten or returned to the back of the swap chain for further processing.