WordPress, like any software, will periodically be updated for security and bug fixes. It is important, not only for securing your WordPress website from hackers, but also for the security of every other account on the server your site is hosted at that you keep your WordPress website code up to date.
WordPress's latest versions will now automatigically update the core files when a new version comes out. It will not, however, update your plugins automatigically. Below are some instructions on how to update your WordPress site if you log into your admin and see there is a notice that you need to upgrade.
The first thing you will want to always do is back up your database. Why? Because if there is an issue with your upgrade, you have the backup to fall back on. In fact, it is really a good idea to backup your COMPLETE website, which includes database AND files. Look under Back Up My Website for details on how to do a full website backup.
If you have more than one database in your hosting account, you will need to isolate which database is being used for your WordPress website. To do this, log into your cPanel, click on the File Manager Icon, then drill down to where your WordPress is installed. (eg: it could be under public_html/blog folder or could be in the "root" public_html folder,) In that folder, you will see a file named wp-config.php. Click the file name and at the top of the screen, click the "view" button. See the graphic below that shows you where the database name is:
Once you have the name of the database, click the home button in your cPanel and click on the Backup icon as shown below
Scroll down on that page until you see the database(s) listed. 
Click on the database name in order to download the database. A window will pop up that will allow you to download the database and save it to your computer.
Once you have your database and/or website backed up, log into your WordPress admin and click on the link to upgrade your installation
Once the WordPress is upgraded, you will want to click to upgrade the plugins
