Record IDs and standard system fields on every object
Key Takeaway
Every record has a unique record ID that never changes. The 15-character ID is case-sensitive and the 18-character ID is case-insensitive, so don't use 15-character IDs in case-insensitive applications.
Every Salesforce object, standard or custom, comes with a few standard fields: an identity field (the record ID), read-only system fields, and a name field. These standard fields and the two record ID formats matter when you design data models, build formulas, and move data in and out of Salesforce without errors.
Objects, fields, and records
In the Salesforce data model, objects are like database tables, fields are like columns, and records are like rows.
Fields you add yourself are custom fields, unlike the standard identity, system, and name fields. Custom field names end in __c (for example, Price__c).