It's a movie rating system used in the United States and Canada, indicating that the film contains some material that may be unsuitable for children under 13. This could include:
* Mild violence
* Strong language
* Suggestive content
* Drug use
* Frightening scenes
However, it's important to note that a PG-13 movie is not necessarily unsuitable for all children under 13. It's ultimately up to the parent or guardian to determine whether or not their child is ready for a particular movie.