OData query syntax is a standard way of querying RESTful APIs using a pre-defined syntax that allows the calling client to define the sort order, filter parameters and pages of data that is returned. The full syntax can be found in section 5 of the OData Version 4.0 Part 2 specification.
Here are a few examples on the syntax use:
The $select option specifies a subset of properties to include in the response body.
The $top query option requests the number of items in the queried collection to be included in the result. The $skip query option requests the number of items in the queried collection that are to be skipped and not included in the result.
The $filter query option specifies an expression or function that must evaluate to true for a record to be returned in the collection.
The $orderby option sorts the results.
I hope this post shows that OData query options can be extremely powerful to supplement your api calls especially for optimization.