This applies both the local nursery or garden center stock and mail order. When you shop trees locally, you are assured that the garden center carries only those varieties best suited to your immediate climate. When catalog shopping, you'll have to do your homework by checking for a pollinator, climate limitations and bloom dates. Be aware that some varieties were developed for cooking, canning, some that keep in the root cellar for months and more than are best eaten fresh. Consider your needs and choose accordingly.
Timing is also very important.
For a single type of fruit there may be dozens of varieties that bloom and fruit at different times during the season. Among the peaches, Stark's Early Giant White ripens in July while the later Encore ripens in September. This is critical where spring comes late because trees must bloom after most of the rain, snow, frost or hail has passed. Bad weather may prevent the flowers from being pollinated. On the other hand, warmer climates may lack enough winter cold for some fruit tree varieties that require a period of chilling or they simply don't produce.