Global Temp Table:

Global temp table starts with ## operator such as ##table1.

They can be used by all other sessions .

Anyone can modify or read data , so you have to be careful !

Global temp table gets destroyed when the creating session is closed or disconnects.

Local Temp Table: 

Local temp table starts with # operator such as #table1.

Local temp tables can be used by only the session which created it and no other session can see or access it.

It is destroyed when the creating session is closed or disconnects. Also , in the creating session , it is only accessible to the level of batch it is created into and automatically destroyed when the temp table goes out of scope of the level.

All temp tables are created in TempDb database of the SQL.

• 6. Programmable Objects