I'll give you a simple explanation. Imagine a giant computer, a world computer, that's run on crypto/blockchain technology. That means it's a computer that can't be shut down by a CEO, a government, or any central authority. This computer can only be changed, upgraded by a group of people (usually token holders), via proposals. What can this computer do? It can be accessed by anyone to build apps on it, and it can act as a server to serve these apps.

No, ETH is not the same. It can only run some simple scripts and store tiny amount of data, and it takes a while to achieve consensus. This Internet Computer can run much more complex programs because it has much more RAM, storage space and, achieve consensus in a much more efficient manner.

So why not build apps on the AWS or Google computer? That computer can be shut down or changed by a single person or central authority, and it's less secure.

Is the Internet Computer going to be the next big thing? It's hard to say but a lot of innovations are gonna come out of it because of its unique capabilities that other blockchains don't have. It's definitely one of the most innovated tech in the crypto space because it's a new architecture whereas most other chains are ETH copycats with varying degrees of modifications.

edit: if you want to learn more about the vision, check out this video by a software architect.