Global temp tables name starts with double hash (##) in sql server. Once this table is created in database, it is like a permanent table in tempdb->temporary tables. It is always ready for all users and not deleted until the total connection is withdrawn.
Local temp tables are only available at current connection time in sql server database. It is automatically deleted when user disconnects from instances. It is started with hash (#) sign.
Anupam Mishra
26-Feb-2016