Custom objects versus fields on standard objects
Key Takeaway
Add a custom field when each existing record needs one more piece of information. Create a custom object, related to the standard object, when you need a new kind of record that can repeat many times for one standard record and needs its own object-level access.
Salesforce comes with standard objects, such as Account, Contact, Lead, and Opportunity, that hold common business data. When those objects don't capture everything a company needs, an admin can add custom fields to a standard object or build a new custom object. A custom field adds a new piece of information to an existing object. A custom object adds a new kind of record that is unique to the company. The choice decides how the data is stored, how it relates to other records, and who can see it.
Objects, fields, and records
In Salesforce, an object is like a database table, a field is like a column, and a record is like a row. The data model is the collection of objects and fields in an app.
Standard objects, such as Account, Contact, Lead, Opportunity, and Case, come out of the box with Salesforce. Custom objects are objects that you or another admin create to store information specific to your company or industry.