A VPS is a private, virtual server that exists on a much more powerful physical machine. But unlike shared hosting, you have a guaranteed allotment of system resources that only you have access to.
So, even if there is a much bigger website than yours on another VPS, hosted on the same physical machine, that won’t matter: you’re always guaranteed the system resources that you’re paying for. Think of it like one big computer, running lots of little computers inside of it.
This means that provided you don’t overtax your VPS, your website will perform faster. when your website grows further, you can upgrade your VPS to a dedicated or physical server in a matter of minutes – no migration required.