A point of sale display or POS display is a special type of display used in stores or shops to show you things you might want to buy. It's usually placed close to the area where you pay for your shopping.
Let's say you go to the store to buy some chocolates. You go to the cash register to pay for them, and then you see a display of more chocolate bars right in front of you. That's a point of sale display.
It is made to get your attention and encourage you to buy more things which you might not have intended to purchase initially. It’s like a special advertisement that's trying to get you to look at other stuff you could buy.
The point of sale display can be a stand-alone shelf, a wooden or metal rack or even a poster. They come in different shapes and sizes, some are small and some are big. POS displays can show special deals, new products or things that are on sale.
In short, a point of sale display is a special little store display that tries to get you to buy more things by showing you other things you might like at the checkout counter.