With every new release of the WordPress software, you get a range of improvements and upgrades. Some of those are entirely new features, some are improvements to old features, and some are improvements in the realm of security. For that reason, keeping your WordPress up to date is the best way to stay out of trouble and make sure that your WordPress website remains in tune with the current developments in website security.
Whenever a new version of WordPress is available, you'll see an update prompt in wp-admin. Please make sure to pay attention to those prompts. It really can't be emphasized enough how important they are.