The cloud is, at its core, consuming computing as a service: instead of buying and running your own servers, you rent capability from a provider over the internet and pay for what you use. The key distinction is how much you manage, captured by three models. IaaS (Infrastructure as a Service) rents raw infrastructure — virtual servers, storage, networking — and you manage the operating system and everything above it. PaaS (Platform as a Service) rents a ready platform to run your applications, so you manage the app but not the servers under it. SaaS (Software as a Service) is finished software you just use — email, a CRM, a document suite — and you manage almost nothing technical.

The trade-off is simple: the higher you climb toward SaaS, the less you manage but also the less you control. SaaS is fastest and easiest but you accept the provider's choices; IaaS gives the most control but hands you the most responsibility. Most small organizations lean heavily on SaaS (like Microsoft 365, the focus of this level) precisely because it removes the burden of running infrastructure. The cloud also changes the cost model — from big up-front purchases to ongoing subscriptions — and shifts, but does not remove, your responsibilities: security, data and access are still yours to manage. Understanding these models lets you choose the right level for each need and know exactly where your job begins.