Vlad Drumea performs a deep dive:
In SQL Server, IDENTITY is a column-level property that is used to provide an auto-incremented value for every new row inserted.
All you have to do is provide a seed value and an increment value when defining said column, and SQL Server will handle it from there.
Unlike sequences, identity columns do not require additional objects like default constraints or triggers to ensure the column is populated.
I’m glad that Vlad made a demo showing how @@IDENTITY works and how it can give you unexpected outputs if you’re not aware of a trigger working with a separate identity column. That one tends to get people.