It’s basically another board that you attach to a Raspberry Pi or similar SCB that allows you to gain additional functionality like adding sensors, cooling, more ports and so on.
Here’s one example: (click). The green board at the bottom is a Raspberry Pi Zero (I think) and the blue board on top is a hat, specifically a Sense HAT. It has additional sensors like one for temperature, a gyroscope, barometer, etc.
It’s basically another board that you attach to a Raspberry Pi or similar SCB that allows you to gain additional functionality like adding sensors, cooling, more ports and so on.
Here’s one example: (click). The green board at the bottom is a Raspberry Pi Zero (I think) and the blue board on top is a hat, specifically a Sense HAT. It has additional sensors like one for temperature, a gyroscope, barometer, etc.