A WordPress website is constructed of:
These allow you to build whatever you like in whatever style you choose with unlimited functions. The developers of WordPress, themes and plugins are constantly working in the background to update and bring new technology and designs to their products. These come in the form of updates and will show on the updates page of your WordPress dashboard.
Updates are a change in the code of the theme/plugin and when updates are released developers of compatible products need to update and rewrite some of their code to make sure everything works together. They will then release their own updates which, again you’ll see in the updates section of your dashboard or if you’re using one of the security plugins it will email and tell you.
If you don’t run your updates regularly, and by regularly I mean monthly, you could be exposing your website to attacks where a change in the code has made the site vulnerable. If you’re not confident in doing this you can turn on ‘automatic updates’. Just be sure in all circumstances to keep a back up of your site.