Hosting Models
IaaS
Infrastructure as a Service rents raw building blocks (compute, storage, networking) that you assemble and manage yourself.
IaaS rents the raw ingredients: virtual machines, block and object storage, networks, load balancers. You assemble them into whatever you need and manage the operating system and everything above it. It's the most flexible cloud model and the one that demands the most from you.
Every major cloud is IaaS at its core. AWS, Google Cloud, Azure, and Oracle Cloud sell it with hundreds of adjacent services. DigitalOcean, Vultr, and Linode sell a stripped-down, developer-friendly version of the same idea without the sprawl.
Compared with a PaaS, IaaS gives you control and takes back convenience. You decide the runtime, the scaling, the patching. That's power if you have the skills to wield it, and a liability if you don't.