An API, or Application Programming Interface, is a set of rules and protocols that allows different software applications to communicate with each other. APIs provide a way for developers to access the functionality of another piece of software, such as a web service, and use that functionality in their own applications. APIs are used for many reasons, including:

Simplifying development: By using APIs, developers can access the functionality of other software without having to understand the details of how that software works. This can save time and effort when building new applications.

Enabling integration: APIs allow different software applications to work together, even if they weren't originally designed to do so. This can help businesses integrate their systems and data, improving efficiency and productivity.

After completing this module, you'll be able to:

Describe the two model types of APIs in ASP.NET Core.

Create Swagger documentation for an API by using Swashbuckle.

Interact with an API by using the Swagger interface.

Experience writing C# at an intermediate level

Ability to write HTML at an intermediate level

Knowledge of RESTful services and HTTP action verb

Read more:- https://learn.microsoft.com/en-us/training/paths/develop-asp-core-api/