External object capabilities
Key Takeaway
An external object behaves much like a custom object, but its records stay in the external system, and it is read only by default.
External objects let Salesforce users see and work with data that stays in another system. App builders need to know what external objects can do, how they relate to other objects, and which platform features they don't support.
What an external object is
An external object is similar to a custom object, except that its data is stored outside your Salesforce org. Each external object maps to one data table in the external system, usually with Salesforce Connect. Each of its fields maps to a column in that table. The external object relies on an external data source definition for its connection details.
Salesforce Connect is available in Developer Edition, and for an extra cost in Enterprise, Performance, and Unlimited Editions.