Virtual machines (VMs) and containers are both technologies that can be used to host applications in an isolated environment. However, they differ in how they achieve isolation and the level of abstraction they provide.

Virtual machines are a type of software that emulates a physical computer, creating a separate and self-contained operating system (OS) environment for the hosted application. Each VM includes its own OS, system libraries, and system tools, which means that VMs are relatively large and require a lot of resources to run.

Containers, on the other hand, are a lightweight alternative to VMs that provide a way to package and distribute applications. Instead of emulating a full OS, containers share the host OS kernel and rely on system libraries and tools provided by the host OS. This means that containers are much smaller and more resource-efficient than VMs.

So, when should you use a VM and when should you use a container? Here are some factors to consider:

• Resource utilization: If you need to run multiple applications on a single physical server, using containers can be a more efficient choice because they use fewer resources than VMs.
• Isolation: If you need strong isolation between the hosted application and the host OS, a VM may be a better choice because it provides its own OS environment. However, if you just need to isolate the application from other applications on the same host, a container may be sufficient.
• Compatibility: If the application you are running requires a specific OS or specific system libraries and tools that are not available on the host, you will need to use a VM because it provides its own complete OS environment.
• Deployment: If you need to deploy your application to multiple environments (e.g., test, staging, production), containers can be a good choice because they are portable and can be easily moved between environments. VMs, on the other hand, may require more customization to work in different environments.

VMs and containers are both useful technologies for hosting applications, but they differ in terms of resource utilization, isolation, compatibility, and deployment. Choosing the right one will depend on your specific needs and requirements.