Topics are subgenres
and/or themes of any kind (i.e.: Romantic Comedy, Friendship, World War II, Sports, and so on.) that enable you to define more specifically
the plot of the movie you are looking for. Topics are not keywords: If you search for a given topic, 'Sharks' for example, only movies in which sharks play a significant roll will appear, such as 'Jaws', not every movie that has a shark in it.
We already have more than 300 topics at Filmaffinity.