what is ## infront of table in sqlserver

## represent global table and # represent local table.
Both represent temp table.
In both case temp table create in Temp database.
Both type temp table accessible in different store procedure.

Now question arise when both have same working then what are differences in local temp table and global temp table?

The global temp table(##) is accessible for different user login with same data but local temp table(#) has data for particular user login. means the difference is for different user use same table(##) and different users have different temp tables(#).

Hope It will be helpful.