The idea is that there are lots of things in our homes that could benefit from being a little smarter. A coffee pot that is linked to my alarm clock so my coffee is always ready when I wake up (for example). Currently we can put a timer into a coffee pot but we can't make it talk to the other things in the house.
The internet of things is the process of putting a computer processor and a wi-fi connection into these kinds of everyday items so that we can use computer programming to control those devices. This allows us to create solutions where the devices communicate and work together.
But this is the simplest explanation for such a complex technology. If you want to know more, I recommend reading this article
https://www.sam-solutions.com/blog/iot-testing/ Here you will learn more about what the Internet of Things is and how it is tested.