Two ways that an administrator can query Order Summaries using APIs in Workbench are:

Platform API. The Platform API is a set of REST and SOAP APIs that allow developers to access data

and functionality in Salesforce from external systems. The Platform API includes various resources

and operations for querying, creating, updating, or deleting records in Salesforce, such as Order

Summaries. The administrator can use the Platform API in Workbench by selecting the REST Explorer

or SOAP Explorer tabs, and entering the appropriate request URL and parameters.

Composite API. The Composite API is a type of REST API that allows developers to execute multiple

subrequests in a single HTTP request. The Composite API includes various resources and operations

for batching, tree, sObject collections, or transactions in Salesforce, such as Order Summaries. The

administrator can use the Composite API in Workbench by selecting the REST Explorer tab, and

entering the appropriate request URL and JSON body.

Verified Reference: https://developer.salesforce.com/docs/atlas.enus.api_rest.meta/api_rest/intro_what_is_rest_api.htm

https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_composite.htm