Traditionally, organizations need to take care to provision specific infrastructure for their services. Whenever our applications need to scale, we need to buy more servers for them, many times using costly hardware provided by different vendors, and tanking a considerable amount of time to configure them within our systems.
That infrastructure approach usually is tied to a static capacity, so if we have a peak of load in our app, we need to buy more servers, and after that peak is gone, part of our infrastructure is unutilized, sometimes producing more costs just to maintain it or recycle into new services, and because configure isn't easy, probably we keep it as-is until the next peak comes in. Cloud computing is about using common and cheap hardware to create resources that could be used to dynamically deploy and run multiple applications that can be scaled either automatically or manually.
In a traditional architecture, we may have a database that has a certain capacity and is running in a particular server; if we need to scale it, we either upgrade the server resources, or we buy another server and configure. In a cloud, we create a database server and we scale the number of instances dynamically, and we get rid of unused instances if we don't need them anymore. The resources freed on the cloud could be used for creating or scaling other applications, and the cloud capacity overall could grow just by adding more conventional servers to it.
This approach allows organizations to go to a pay-as-you-go model for their infrastructure, instead of up-front buying servers, they could pay whatever resources their need for a specific period of time. Cloud applications are designed to easily be configured, since the overall idea is to have services that could be easily spawned in a short time. Cloud Native applications will use some kind of system, either provided by the cloud platform or the application itself, to be configured when new instances are created. Since we need to have services running in our cloud that could easily spawn and destroy, the majority of cloud use some kind of containerized applications.