you give no clue to location. One way to guess, if they are blooming very early for "spring" in your location, then probably ornamental. Ornamental cherries are some of the first trees to blossom. One answer is see if they produce cherries. However, if the bees fly late or they are of a type that needs a pollinator variety, they could be fruit cherries and never bare. Also cherries trees take many years to start bearing if they are full size or even semi-dwarf, so the tree could simply be to small to bear. If you are new to this place maybe one of the neighbors knows what was planted.