Alright kiddo, let me explain this to you in a way that you will understand.
So imagine you and your friend are playing with your favorite toys, and one of your toys accidentally breaks your friend's toy. Your friend gets upset and wants you to give them a new toy to replace the one that broke.
This is kind of like what happened between Anderson and Stallone, but with grown-ups and more serious stuff. Anderson sued Stallone because he claimed that Stallone stole his idea for a movie and used it to make a big hit movie.
It's like if you and your friend were both coming up with ideas for a fun game and you told your friend your idea, but then your friend made the game without giving you credit or sharing the toys.
Anderson believed that Stallone should have given him credit and maybe even some money if his idea was used to make the successful movie.
So they went to court to try and figure out if Stallone really did steal Anderson's idea or if it was just a coincidence that the two movies were so similar.
Does that make sense, kiddo?