The REST API is a popular way to interact with web-based systems, including Salesforce. It is based on the principles of Representational State Transfer (REST) and uses standard HTTP methods to interact with resources.

A REST resource is a representation of information or action, such as a single record or a collection of records. Each resource in the REST API is identified by a unique Uniform Resource Identifier (URI) and can be accessed through standard HTTP methods such as GET, POST, PATCH, and DELETE.

When making a request to a REST API, there are four components to consider: the resource URI, the HTTP method, request headers, and the request body. The resource URI is the identifier for the resource you want to access, the HTTP method specifies the type of action you want to perform, request headers provide additional information about the request, and the request body holds the data for the request.

Using the Salesforce REST API, you can perform various actions such as retrieving information about the available API versions, obtaining details about objects like Accounts and Users, performing searches and queries, and updating or deleting records.

In summary, the REST API is a powerful tool for accessing and interacting with web-based systems, including Salesforce. It operates based on the principles of REST and uses standard HTTP methods to access resources, which are identified by URIs. When making a request to the API, you must consider the resource URI, HTTP method, request headers, and request body to ensure proper interaction with the system.

In this article, we will be exploring the use of Postman for making API calls to Salesforce. Postman is a popular tool used for interacting with APIs, and it allows you to make REST requests from any HTTP sender.

To get started, you will need to create a new Trailhead Playground, connect it to the Postman app, set up cross-origin resource sharing, and create a fork to the Salesforce API Collection. This process can be completed by following the Quick Start guide: Connect Postman to Salesforce.

Once you have set up the connection between Postman and Salesforce, you can make REST API calls to your Trailhead playground using the resources in the Postman Salesforce Collection REST folder. When you select a resource from the Salesforce API Collection, the URI will be displayed across the top of the main window in Postman.

Now, let's take a look at how to use the Postman app to describe the Account object in Salesforce. You will be using the SObject Describe resource, which, when combined with the GET method, returns metadata about an object and its fields.

Here's how you can describe the Account object:

• In the Collections section of Postman, select your fork of the Salesforce APIs Collection.
• Navigate to the REST folder.
• Click on the SObject resource.
• Select the GET SObject Describe method.
• In the main panel, open the Params tab.
• Under the Path Variables section, in the SOBJECT_API_NAME row, enter "Account" in the VALUE column.
• This is just one example of how you can use Postman to interact with Salesforce through the API. By exploring the resources available in the Salesforce API Collection, you can perform a wide range of actions and gain insights into your Salesforce org.