The most obvious and popular reason for a VPS is to run a single website, or multiple websites. However, you can use them for pretty much anything that requires access to the internet – such as a web application like Nextcloud to run your own Dropbox alternative – or to create your own virtual private network to better secure the internet connection of your PCs and mobile devices.
Shared hosting is a simple option to set up a site and start accepting visitors ASAP. Unfortunately, it can quickly backfire when websites grow in popularity because more resources are consumed and more sessions are delivered each moment. Eventually, things can come crashing down or slow to a crawl.