There's one point in particular that took me a while to grasp: while you can write code that runs on the Ethereum network, every single node has to process that code.
So if, for example, you had a big 3d animation sequence that you wanted to have rendered, you would not just send that code off to the network to be processed. You would have to pay to have every single person on the network process that job for you, and it would be so big the network wouldn't even accept it. Rather, you would create a simple contract that says "if you render this animation for me and prove that you did it right, I'll pay you X amount of Ether". Someone would take the job and the Ethereum network would process your contract and handle the payment. You would end up paying that person to do work for you, and you'd pay the network (using something called gas) to process the contract.
You could use Ethereum to create all kinds of interesting contracts for financial purposes, voting systems, insurance, or whatever else. But it's not some giant compute cluster that will run some big program for you.
So if, for example, you had a big 3d animation sequence that you wanted to have rendered, you would not just send that code off to the network to be processed. You would have to pay to have every single person on the network process that job for you, and it would be so big the network wouldn't even accept it. Rather, you would create a simple contract that says "if you render this animation for me and prove that you did it right, I'll pay you X amount of Ether". Someone would take the job and the Ethereum network would process your contract and handle the payment. You would end up paying that person to do work for you, and you'd pay the network (using something called gas) to process the contract.
You could use Ethereum to create all kinds of interesting contracts for financial purposes, voting systems, insurance, or whatever else. But it's not some giant compute cluster that will run some big program for you.