Short answer
A Salesforce sandbox is a copy of your production org used to build and test changes safely. Developer and Developer Pro sandboxes copy configuration only, Partial Copy sandboxes add a sample of data, and Full sandboxes copy all data, so teams can test with realistic records before anything reaches users.
Salesforce Sandbox explained
Changes are usually built in a Developer sandbox, tested with sample data in a Partial Copy sandbox, and given final user testing in a Full sandbox before deployment to production. Each type has different storage limits and refresh intervals: Developer sandboxes can be refreshed daily, while Full sandboxes can only be refreshed every 29 days.
Which sandboxes you get depends on your Salesforce edition and add-on licenses. Full sandboxes are often an extra cost, which is why the question comes up in almost every scoping conversation.
How Vantage Point helps: we set up a sandbox strategy and release path (build, test, UAT, production) sized to your licenses and the risk of each change.
Frequently asked questions
What is the difference between a Partial Copy and a Full sandbox?
A Partial Copy sandbox holds your configuration plus a sample of records defined by a template, up to a storage limit. A Full sandbox is a complete copy of production data and metadata and is the best place for final user acceptance testing.
Why does my sandbox have fewer records than production?
Developer sandboxes copy no data and Partial Copy sandboxes copy only a sample. Only a Full sandbox mirrors production record counts.