What does the "#" symbol in TSQL mean?

Question

Or "octothorpe" for the pedants :)

Google says "non-sharable temp table" but I don't know what that means. Any clarification would be helpful.

Thanks

Answer 1

It creates a temp table that is visible to the current scope, and can't be accessed across logins. It gets cleaned up once it's out of scope (i.e. the stored proc is finished running).

If you define a temp table with "##", it is global, and can be accessed across sessions.

Answer 2

It creates a temporary table that can only be accessed during the current session (login).

You can also create global temporary tables that are accessible across all connections by prefixing the table name with ##.

See here for more details.