Pan and scan when talking about DVDs is refered to primarily as making a widescreen image appear correct in a standard screen. So Pan and Scan is geared towards 4:3.
If you play it on a widescreen TV it is stretched as hell.
Pan and scan is a generic term though and it also refers to making 2:35 material fit in 16:9 as well, but with DVDs we are talking 4:3....