Failed to understand following code

SET stringIndex = INSTR(filterText, 'State1') - 8; // what this line is doing??


/* what is following block of code is doing */
set @sql=
CONCAT('
Create TEMPORARY TABLE tblGeo
(SELECT Distinct State, District, Code FROM tblStateDistrict WHERE Country = ''India'');
');

PREPARE stmt FROM @sql;
EXECUTE stmt;