Win the buy box while keeping your margin
When several sellers offer the same product, one of them gets the "Add to basket" button: the buy box. Whoever has it sells the most. Price is one of the things bol looks at, along with delivery time and your quality score.
The repricer makes sure your price is sharp when it counts, and that you don't stay needlessly cheap when you don't have to. You choose whether it goes just below the competitor or matches their price, and with what step (default € 0,10).