Often times it is very confusing to distinguish between - “What is an Application?” and “What is a Service?” and what should I be saying from a terminology perspective?

What is a Service?

• A service is something that does just one thing (mostly!)
• Does not have a UI
• Exposes an API typically

What is an App/Application?

• Does many things (mostly!)
• Does have a UI (WebUI, Mobile, CLI, etc)

Application calls multiple services behind the scenes. Say https://www.google.com or http://amazon.com - WebUI would call a bunch of services to serve the page with content.

Container Perspective

With Cloud-Containerization (Kubernetes) becoming ubiquitous for all developments; it would be safe to say with the above that Kubernetes-cluster will not host Applications, but will host Services that Applications will consume!

An illustration with a diagram:

In Summary, if it is a UI and does many things then it is an App/Application and if it is no-UI and does one thing only and one thing well then it is a Service.

Reference:

• Kubernetes - Scheduling the Future at Cloud Scale