Understanding "VPS"

As my site is growing, I've been advised by fellows here in WHT that I need to upgrade to VPS.

After little research, I got an idea in theory about how it works. But still have very basic questions;

1. As known there are managed and unmanaged (self-managed) services. Say that I got a fully managed plan that includes a cPanel+WHM, would I need extra skills other than skills required for managing website on a shared host? Would I need low-level commands or server side stuff? In other words, can I just use cPanel, FTP, file manager, etc to upload files, manage emails, FTP accouts, and just do everything exactly as done on a shared host? Note that I will use only single website so I don't need to worry about multiple accounts on the plan.

2. In theory, a shared host means many websites share a server including its resources. In VPS, also, a number of clients run on a single server (it not like dedicated). So, then what's the main difference between shared host and VPS?

For 1st question, if you reckon that "management" may vary between different providers, I can give you specifically what service I'm planing to have:

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