With unmanaged VPS hosting, the cost is also much cheaper. It is not uncommon to find $10 unmanaged VPS plans because the web host does not have to pay for a cPanel or Plesk license and are able to minimize costs. Also, since the web host does not provide software and account support for an unmanaged VPS, the host also saves money on customer support. In the end, you'll have VPS hosting that is typically $20-30 cheaper than a managed VPS solution.
All the features I've detailed to this point are valuable to the web hosting experience, but none matches the critical importance of site uptime. If your site is down, clients or customers will be unable to find you or access your products or services. It doesn't matter how great the features are, or how good it looks; if your site is down, it might as well not exist.
A VPS runs its own copy of an operating system (OS), and customers may have superuser-level access to that operating system instance, so they can install almost any software that runs on that OS. For many purposes they are functionally equivalent to a dedicated physical server, and being software-defined, are able to be much more easily created and configured. They are priced much lower than an equivalent physical server. However, as they share the underlying physical hardware with other VPSes, performance may be lower, depending on the workload of any other executing virtual machines.