White and black peppercorn are both derived from the same berry of the peppercorn plant. However, in the case of white peppercorn the berry is allowed to fully ripen before harvesting. It is then fermented so that the skin of the berry can be removed.
The naked kernel then dries in the sun before being shipped to market. It is more popular in Europe than North America where black peppercorn is preferred. In America, whole white peppercorn is sometimes found in the peppercorn mixes meant for grinding as needed into dishes.
There it mostly provides a visual complement to the black, and sometimes green, or even red berries that are also included in the mix. It should be noted that though black and green peppercorn are both same species as white peppercorn, but pink peppercorn is from a different plant entirely. The taste of white peppercorn is a little more subdued than black peppercorn.
It has a slightly milder flavor, with less complexity and less heat.