Q:

Understanding Cloud Instance per hour

I am getting to be into Cloud Computing, but I am really confused in what it means instance.
In programming you can call an instance whenever you call an object, for a Machine it's a server, but here I can tell it's different, there's where I get confused.
So basically what I need to understand is:
- What is an instance per hour?
- How does it work?
- If I have an app (web app), how can I measure an instance, to calculate the hourly pricing?
Can someone explain this to me as simple as possible? too many tutorials on google and still not getting it
Thanks,
;)
Update: I found this postWhat do 'instances' mean in terms of cloud computing?
And it's useful because someone answered exactly what I need to understand:

  For App Engine it's not a VM; it's a process. – Guido van Rossum Aug 21 '12 at 3:38

So how can I calculate by process?

A:

The question is a bit vague. My answer is based on the amazon-web-services tag and the phrase "What is an instance per hour".
In the Amazon cloud, you can rent 'EC2' servers. EC2 stands for elastic compute cloud: Amazon's lingo for a virtualized server in the cloud.
An 'instance' is one running EC2 server: one running VM. "Instance per hour" refers to the pricing (as described on https://aws.amazon.com/ec2/pricing/). You generally pay-per-use on an hourly base: When the "price per instance per hour" is $1 and you run 1 instance for 4 hours, you pay $4.
When you want to run a web app, you pick an instance type based on memory, cpu capacity and storage type (although you can add storage separately) that's a good fit for your web app, launch the instance and deploy your web app to it.

