1. IaaS (Infrastructure as a Service)

• Description: Provides basic infrastructure resources like virtual machines, storage, and networks over the internet.

• User Responsibility: Users manage the OS, applications, runtime, and data, while the cloud provider manages the physical infrastructure.

• Use Case: Ideal for businesses needing to manage their own applications and operating systems but want flexible, scalable infrastructure without hardware maintenance.

• Examples: AWS EC2, Google Compute Engine, Azure Virtual Machines.

2. PaaS (Platform as a Service)

• Description: Offers a platform with development tools, databases, and runtime environments, simplifying application development without managing underlying hardware or OS.

• User Responsibility: Users focus on application logic and data while the provider handles OS, runtime, infrastructure, and scaling.

• Use Case: Useful for developers who want to build and deploy applications quickly without worrying about infrastructure management.

• Examples: Google App Engine, AWS Elastic Beanstalk, Microsoft Azure App Services.

3. SaaS (Software as a Service)

• Description: Fully managed software solutions that users access via the internet, with everything from infrastructure to application managed by the provider.

• User Responsibility: Limited to using the application; all maintenance, updates, and infrastructure are handled by the provider.

• Use Case: Best for end-users who need a ready-to-use application (like email or CRM) without technical setup.

• Examples: Gmail, Salesforce, Microsoft Office 365, Dropbox.