Most coffee cherries contain two seeds with a flatter inner surface. A peaberry develops as one relatively rounded seed instead. Producers may separate these beans from the rest of a crop and sell them as a distinct lot, making the shape visible in a product description.
Sorting adds work, and a more uniform size and shape can matter to a roaster's handling of a batch. Those practical considerations do not establish that every peaberry tastes more intense or better than the corresponding flat beans. The source itself notes that the difference in the cup may be modest or absent.
For a buying decision, ask for the actual lot information, roast date and tasting description. If you want to explore the distinction, compare coffees from the same producer and crop where available. Brewing two unrelated origins would introduce too many other variables to isolate the effect of seed shape. Treat a peaberry premium as a reason to ask questions, rather than as a substitute for choosing a flavor you enjoy.
The conversation
A good question can make a better brew.