The key difference between remotely-hosted, virtualized, on-demand-by-API servers (the definition of the “cloud” for this post) and any other hardware-based deployment (e.g., dedicated, co-located, or not-on-demand-by-API virtualized servers) is that servers are software on the cloud. Software applications traditionally differ from server environments in several key ways:
1. Traditional servers require humans and hours–if not days–to launch; Software launches automatically and on demand in seconds or minutes
2. Traditional servers are physically limited–companies have a finite number available to them; Software, as a virtual/information resource, has no such physical limitation
3. Traditional servers are designed to serve many functions (often because of the above-mentioned physical limitations); Software is generally designed to serve a single function
4. Traditional servers are not designed to be discarded; Software is built around the idea that it runs ephemerally and can be terminated at any moment
"— The Advantage of Cloud Infrastructure: Servers are Software - ReadWriteCloud
