A schema is a collection of database objects (e.g. tables, views, stored procedures, …) that enables easier organization and access control.
In SQL Server, the default schema is dbo, which stands for “database owner.” SQL Server treats schema the same as a regular database. Meanwhile, in PostgreSQL, schema is a subdivision or namespace of a database, so we might create a user schema with tables related to user management. PostgreSQL schemas can also be used for multi-tenant data isolation—each tenant is a schema (you would have to recreate necessary tables for new tenants).