REST API call & endpoint
CiviCRM provides api for each entity. Each entity has its own parameter. You can use API explorer to find how params are build and need to send through rest api. The API explorer screen provides detailed information about using various method of using api to perform CRUD operation on CiviCRM. 

While using rest api you will need to pass Site key (stored in civicrm.settings.php) and User contact's api key (You can either set this in civicrm_contact table or use API Key extension to set and see the api key) as part of authentication. 

Cheers

Pradeep