REST API is how frontend and backend part of applications talk to each other, different apps communicate, how CLI tools talk to web services. It is a vital part of modern apps.

Learn about API and know how to consume(or use) APIs of cloud providers, git hosting and other services, create your own and let others interact with your applications with API.

Using API you can automate a lot of day to day tasks and build one-person businesses by leveraging this technology.