The BitBlt API:
BitBlt is a function in the DLL "gdi32".
Technical Deffinition:it performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context.
In Plain English...This basically means that it copys graphical data from one graphics surface [a bitmap] to another graphics surface [the screen,or a form].
你可以试着翻译一下,应该就是 bit-block transfer的缩写.