Catalysts make reactions go faster and are not consumed during the reaction. There are molecules that are mirror images of one another. It was thought that there were only two types of catalysts that could help with those: enzymes and metal catalysts. The laureates discovered a third type that is easier to work with and outperforms the other methods. It is in wide use now.

(Edit: that turned out to be pretty ELI5 actually. Proceeds to build mirrored molecules from Lego bricks...)