API stands for Application Programming Interface. APIs are used for communication between the frontend and backend of the application. When a user wants some information, a request must be sent to the server. This request is sent to the server using an API endpoint, and it returns the required data. The data is obtained from the database and retrieved in JSON format. APIs also provide security by not exposing the user's data to the server. The different APIs include REST, SOAP, RPC, Open APIs, etc. The back-end technologies used for the development of APIs are Spring Boot, Django, PHP, etc.