AWS is what is known as a cloud provider. Other cloud providers are Microsoft Azure and Google cloud. Cloud providers have big data centers around the world full of servers that they rent out in different ways. You can rent full servers for yourself, or just rent time on a shared server. This is very convenient if you need a really powerful server, you can rent it by the minute. Or if you only need a fraction of a server, you can rent it for cheap. When you rent the really powerful server, that is called “scaling up”.
You can also rent access to software services running on those servers. For example, instead of renting a full server to hold your database, you can just gain access to your own space inside a large shared database.
What is more, if your application suddenly needs more database, then the cloud provider will simple spread your need over multiple servers for you automatically. This is called “scaling out”.
There is a lot of innovation in the offerings of cloud providers, new services that allows you to scale up and out are introduced every day.
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