The page and per_page parameter is used to fetch records according to their position in the CRM. Let's assume that the user has to fetch 400 records. The maximum number of records that one can get for an API call is 200. So, for records above the 200th position, they cannot be fetched. By using the page (1 and 2) and per_page (200) parameter, the user can fetch all 400 records using 2 API calls.
Link: https://www.zoho.com/crm/developer/docs/api/v3/get-related-records.html