Type A and type B refers to when the flowers release pollen and are receptive to pollen since the flowers on the same tree are not on the same schedule. You need both
types so that they pollinate each other for best results.
You'll want to research the variety/cultivars of the two types to see if there are specific recommendations for better fruit production. (they need to bloom around the same time obviously) Do you know what they are selling? Other traits to look for are how big they get and when the fruits mature for harvesting. Best flavor, etc.
Here's one ref. I always seem to end up at this one. Look under flowers for A and B explanation. Some cultivars are listed here as well:
Hey, this looks good. I'm going back to it and browse for a while