“__c” signifies something custom in Salesforce while “__r” signifies a relationship. When you use “__c”, you are telling Salesforce that you need the data that is stored in that particular custom field, whatever it may be.
In short, “__c” signifies something custom in Salesforce while “__r” signifies a relationship. When you use “__c”, you are telling Salesforce that you need the data that is stored in that particular custom field, whatever it may be.