REST stands for representational state transfer and API stands for an application programming interface. REST API is basically used for performing some operations and getting responses based on the request using the HTTP protocol. Magento provides a huge list of REST APIs which you can check here . Another approach to check and play with the existing APIs in the Magento system is Swagger. You can access Swagger by any browser and the URL will be your website's baseUrl/swagger . Now let's see how we can add a new custom API in Magento. Let's learn this by creating a custom API to get all the store configurations using API. Step - 1: Create a webApi.xml file and add the route for your API <?xml version="1.0"?> <routes xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Webapi:etc/webapi.xsd"> <route method="GET" url="/V1/custom/storeConfigurations/"...