Users of Shared hosting all share the resources on the server their on. There is no guarantee of RAM or CPU with Shared hosting. Shared hosting also does not provide full root access to the server, as opposed to VPS package where users are given full root access to perform commands and make configuration changes to their hosting environment.
Simply put, shared hosting means you will share the same server as many other users. It’s usually the cheapest option but comes with limited administration. VPS hosting is a more premium option, with the ability for greater customization and options.