Hi Vijay,

Workbench is a powerful, web-based suite of tools designed for administrators and developers to interact with Salesforce.com organizations via the Force.com APIs. Workbench includes robust support for the Force.com Partner, Bulk, Rest, Streaming, Metadata, and Apex APIs that allows users to describe, query, manipulate, and migrate both data and metadata in Salesforce.com organizations directly in their web browser with a simple and intuitive user interface. Workbench also provides many advanced features for testing and troubleshooting the Force.com APIs, such as customizable SOAP headers, debug logs for API traffic, backward compatibility testing with previous API versions, and single sign-on integration within the Salesforce application.

Please do note that Workbench is NOT a supported product of or supported by salesforce.com, inc. For support from the open source community, please visit the resources below:

We can interact with salesforce data using api's either authenticating from external applications like postman or soapui and accessing the data using session id or token.

For using rest API via rest API then you can check the below link that has a step by step implementation:

>> https://www.sfdcstop.com/2019/01/how-to-connect-to-salesforce-with.html

Let me know if it helps you and close your query by marking it as solved so that it can help others in the future.  

Thanks.