it is a type of composite train where in between some stations (generally the overbight travel) the train acts as express with minimal stoppage and fare charged is that of express where as in between other stations it stops at almost all stations (the day time) and fare charged in between those stations is that of passenger
panch valley passenger if i remember rightly is a composite exp cum passenger
some trains also act as composite sf cum exp like hwh dli kalka mail...