Well, the main difference is that with real casinos, you actually turn up and sit at a table! With a live online casino, however, you’re playing at home using your phone, tablet, or computer.
There are some major similarities, of course. Using a live stream video means you'll watch a real dealer on a real table, in a land-based venue. Typically, the table won’t be in a real casino, however.
Online casinos use studios to simulate a real casino experience, and what you see on the video looks just like a real casino. It’s effectively the same experience, with experienced dealers who understand the game and a totally transparent betting system.
It’s similar, it’s not the same, but it’s the closest thing you can get to actually visiting a land-based casino!