#temp tables are created in the tempdb and are only available during the current connection.  Something like the following would not work:

begin

create #temp

commit

select * from #temp

From BOL:

Local temporary tables have a single number sign (#) as the first character of their names; they are visible only to the current connection for the user; and they are deleted when the user disconnects from instances of Microsoft® SQL Server™ 2000. Global temporary tables have two number signs (##) as the first characters of their names; they are visible to any user after they are created; and they are deleted when all users referencing the table disconnect from SQL Server.