What the cloud is, without the marketing

The cloud is someone else's computers, rented by the hour, with an interface for creating and destroying them in seconds.

That speed is the actual change. Buying a server used to take weeks of procurement. Now it takes a minute, and you can destroy it a minute later and stop paying. Everything else follows from that.

Regions and availability zones. AWS runs data centres in regions around the world, each with several separate zones. Choose the region nearest your users, because distance costs time on every request. For a Pakistani audience, Mumbai or Bahrain are the closest. Choosing Virginia because the tutorial did adds real latency to every visitor, and it is one of the commonest beginner mistakes.

The shared responsibility model decides who is to blame. AWS secures the infrastructure: the buildings, the hardware, the hypervisor. You secure everything you put on it: your operating system patches, your passwords, your permissions, your data. Nearly every publicised cloud breach was the customer's half, usually a storage bucket left public.

Pricing. You pay per hour or per request, plus storage, plus, critically, data leaving AWS. Traffic in is usually free and traffic out is not, and a surprise bill is almost always this.

Set a budget alert before you create anything. Ten minutes of work that prevents a bill you cannot pay. Free tier limits are generous and easy to exceed by accident.