What Is Cloud Computing? Definition, Features, and Service Models

On a weekend at home, the author was reading a book while his girlfriend watched a game livestream; she noticed a confusing comment in the chat and asked, prompting a discussion about cloud computing.

What is cloud computing? The Internet began in the 1960s for military and large‑enterprise email and news groups, reaching households only in the 1990s. As the web and e‑commerce grew, networking became essential for daily life and for enterprises that needed to store operational data for product, personnel, and financial management.

Enterprises initially bought servers, storage, and network services, but a single server soon proved insufficient, leading to the need for more powerful computers or clusters of servers. High upfront costs and ongoing electricity and maintenance expenses made it difficult for small‑ and medium‑size businesses, giving rise to the concept of cloud computing.

On August 9, 2006, Google CEO Eric Schmidt first introduced the term “cloud computing” at the SESSanJose2006 conference. In essence, cloud computing means renting remote servers provided by a vendor to store data and perform computations, turning computing resources into a commodity that can be provisioned on demand, scaled elastically, and paid for based on usage.

With cloud computing, individuals and companies can build websites or software platforms without owning physical hardware, simply by renting cloud servers and accessing cloud resources, which greatly simplifies development and operation.

Key characteristics of cloud computing

Virtualization technology abstracts physical resources (servers, networks, memory, storage) into virtual resources, breaking the constraints of physical hardware and enabling flexible resource allocation.

Dynamic scalability allows computing capacity to be rapidly increased, supporting the expansion of applications as demand grows.

On‑demand provisioning lets users quickly allocate the necessary compute power and resources for specific applications.

High flexibility virtualized resources can run on diverse hardware and operating systems, offering strong compatibility and performance.

Reliability If a physical server fails, virtualization can migrate workloads to other servers, ensuring continuous operation.

Cost‑effectiveness Shared virtual resource pools reduce the need for expensive dedicated hardware, lowering overall expenses while maintaining performance.

Scalability Users can easily expand existing services or add new ones through simple deployment processes.

Cloud service models

Depending on user needs, cloud computing is divided into three service types: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). These models form a cloud stack, each building on the layer below.

IaaS provides virtualized compute resources, storage, networking, and operating systems to individuals or organizations.

PaaS offers a development platform for building, testing, and managing applications over the Internet, providing on‑demand development environments.

SaaS delivers software applications over the Internet on a subscription basis, with the provider hosting and managing the software while users access it via the web.

Future articles will explore the differences among IaaS, PaaS, and SaaS in more detail.