Hi
VPS or Virtual Private Server is a virtual server that is hosted on a physical machine. Usually many Virtual Private servers can be hosted on single a physical server. Each of these VPS are isolated from each other and are managed by "hypervisors". Each of these servers are also able to be rebooted independently and each can also run any kind of OS they want. Therefore it looks much similar to a dedicated server (However dedicated servers are more powerful, more autonomous and hence more expensive than VPS).
VPS has its own advantages. It offers more flexibility than a shared server would do because in the case of a VPS, you don't actually share resources but rather split them into independent portions. Hence it is also much safe than shared hosting. VPS is less expensive than dedicated servers. And even though it is a bit similar to it, you can use a VPS with less technical knowledge than you need to use a dedicated server.
Hope this helped.