DVD is video SACD is audio and can be played back in a CD player at regular CD resolution if it is a hybrid disc. SACD can be played back in an SACD player at high resolution and in most cases surround sound.
DVDA is audio and possibly some video and surround. It can be played in an ordinary DVD player at regular DVD resolution or a DVD audio player at higher resolution.
DVDA is audio and possibly some video and surround. It can be played in an ordinary DVD player at regular DVD resolution or a DVD audio player at higher resolution.