Answer: Tech rehearsals generally are broken down into four types: dry tech rehearsals, tech rehearsals, pick-up tech rehearsals, and paper tech. Their purpose is to fully test all of the technology being used in the performance (lighting, sound, automation, special effects (e.g. pyrotechnics), etc.) to diagnose and prevent mistakes from occurring during the actual performance. They also allow the designers to see how their designs will impact each other (i.e. how the color of a light might affect the look of a costume), and to make final changes. Tech rehearsals are to make sure during the show all tech items will run smooth.
Explanation: ;P