Fields in Salesforce

Fields in Salesforce represents what the columns represent in relational databases. It can store data values which are required for a particular object in a record.

There are 2 types of fields:

Standard Fields:

There are four standard fields in every custom object that are Created By, Last Modified By, Owner, and the field created at the time of the creation of an object.
These fields cannot be deleted or edited  and they are always required. For standard objects, the fields which are present by default in them and cannot be deleted from standard objects are standard fields.

Custom Fields:

The Custom fields which are added by the administrator/developer to meet the business requirements of any organization. They may or may not be required.