They're just sample data to be able to run the query.
It looks like your original table name was "DB.RECORD", so you would replace #testTable with DB.RECORD.
The "tt" is a table alias -- a short name for the table that you can use in the query to indicate which table a column comes from. You can leave the alias "tt" or change it to something like "REC" (short for RECORD) or whatever else you want to use.