Film colorization is when someone takes an old movie that was made in black and white and adds colors to it so that it looks like the scenes are happening in real life.
It's kind of like painting a picture, but instead of starting with a blank piece of paper, the colorizer is starting with a movie that has already been made.
The colorizer will look at each scene in the movie and decide what colors to add to it. They might research what colors were popular during the time period the movie was made in to get a better idea of what things should look like.
Then, they use a computer program to add the colors to each frame of the movie. This can take a really long time because sometimes there are thousands of frames in just one movie!
When the colorization is done, the movie now looks like it was filmed in color instead of black and white. Some people think colorizing old movies is a good thing because it makes them look more modern and more people might want to watch them.
But, other people don't like it because they think it takes away from the original artistic vision of the movie and changes the way it was meant to be seen.