Seconds are ceramics that didn't turn out exactly as I had planned. I love imperfections in my work because they add character, and you can see the human behind it - but the unplanned ones - those guys you get at a discount.
Imperfections can range from slight warping in shape, uneven glaze application, or uneven surface texture. None of them will affect the function of the piece, they are all still water tight and food safe. But artists are crazy and we just like stuff how we like it. The % of discount varies based on the piece. Think of them as quirky ceramic rescue pets.