Okay kiddo, do you know how colors work? You see, there are many different colors in the world and we use different ways to measure and display colors. Rec. 709 is one of those ways!
It's like a set of rules and guidelines for how we should show colors on a TV or computer screen. It tells us which shades of red, green, and blue to use to make all the different colors we see.
For example, let's say you want to show a bright and vibrant yellow on your screen. Rec.709 will tell you which specific mix of red, green, and blue lights you should use to make that yellow look just right. This helps make sure that colors look the same on all different types of screens, like your TV at home or the movie theater screen.
So, rec. 709 is just a fancy way of making sure that colors look good and consistent on all types of screens. Now, wasn't that easy to understand?