WordPress runs a third of the worlds websites but websites just like your computer need to be updated and maintained.
WordPress have updates that need to be installed , there are updates to your plug-ins that need to be updated – WordPress plugins are apps that allow you to add new features and functionality to your WordPress website
There can be updates to the themes ( the way your site looks) that need to be updated
If you fail to do these – things can go wrong , for example your site can go down or be taken over with malware.
So you have 2 choices , you need to learn how to do these from the person that built your site or get someone to regularly check for updates.
Doing your updates helps prevent issues