Okay kiddo, have you ever watched a really cool movie that looked so beautiful and captivating? Well, sometimes the people who make movies put a lot of effort into making them look amazing. They call this "cinematography".
The BAFTA award for best cinematography is a prize that is given to the person who did the best job making a movie look stunning. It's like giving a trophy to the person who painted the prettiest picture for the movie.
The people who decide who wins the award are really good at judging what looks great in a movie. They watch a lot of movies and look at how the camera was used, the colors, the lighting, and even the way the camera moves. They then decide which cinematographer did the best job overall.
So, when a movie wins the BAFTA award for best cinematography, it means that the person who made the movie look amazing did a really great job, and everyone thinks that the movie looks really cool!