Because WordPress is an open source application it has almost unlimited supply of coders and developers that are always working to make the platform better and that means they are mainly constant update throughout containing everything from small fixes, security hole patches and to full features upgrade. This is true for the platform itself as well as the plugins and themes.
How to Upgrade WordPress to the latest version
If you are running a WordPress site, it is very important that it is always kept up to date with the latest versions. Fortunately this is quite easy because WordPress would tell you when an upgrade is available.
When an upgrade is available, you will get the warning message on the top of your WordPress Dashboard and all you have to do to click Update Now and you are taken directly to WordPress updates page. WordPress also warns you to please backup you database and files and once you done all those backups, simply click on update automatically and the update starts. WordPress runs full update process and takes a while depending on the internet connection you have. Once its done WordPress gives you message that it has done its processing, wordpress has been updated and you can now go back to dashboard.