Gross box office = total earnings of the movie by selling tickets. 

This means the more people that watch the movie the higher the box office will be.

this image demonstrates that in recent years the most likely way your film will be successful is if the movie is part of a pre-existing franchise, this is because these film franchises have previously established fans and most commonly are made from pre-existing media that already has a large fanbase.

In addition, most films that are successful are not aged rated higher than 12a as this allows the film to be accessible to most ages without limiting key demographics.

Another common factor is that most successful films are big budget and have well known actors in them to help promote the film to their previously established large fan bases.