Layers of abstraction
IaaS gives virtual machines, disks and networks — you manage the OS upwards. PaaS gives a runtime where you deploy code. SaaS is finished software. FaaS runs individual functions with no server management at all. Higher abstraction means less control and less operational work.
Deployment models
Public cloud is shared multi-tenant infrastructure. Private cloud is dedicated, often for regulation or latency. Hybrid links them, and multi-cloud spreads workloads across providers for resilience or negotiating leverage — at the cost of duplicated expertise.
Shared responsibility
The provider secures the cloud — hardware, hypervisor, physical sites. You secure what is in the cloud — data, identities, configuration, patching. Most publicised breaches are customer-side misconfiguration, typically a wide-open storage bucket or an over-permissive role.