The communal Torah reading is divided into aliyos, sections read (originally and still in some places by, otherwise) on 'behalf' of distinct people, in succession. The Torah is read in a tune, and each verse ends with the same tune — except that, in most synagogues I've been in, the final verse of each aliya ends with a different tune than other verses do. Why the change?
Presumably this is a cue to the oleh that the aliyah is over, and he should begin reciting the blessing. If the kore were to simply stop reading, there would be a few seconds of awkward silence until the oleh is sure that the aliyah is over. Also, a kore who pauses for whatever reason would run the risk of having the oleh start the blessing too early.