Tech Moves are special ability moves in the Real Steel game. Once bought, the player can choose an attack button that they are activated by. The only options are normal attack buttons, so these normal attacks are transformed into Tech Moves by the player holding down a certain button while pressing the button.
There are three different versions of Tech Moves: Normal, Unblockable and Destroyer Moves. Normal moves are fairly fast moves, Destroyer moves take a little while to charge before activating a cutscene to destroy a body part, and there are two types of Destroyer moves: Head and Arm. If they land correctly, they'll activate a cutscene to destroy the part specified. Unblockable moves are moves that take a while to charge, leaving you vulnerable, but if they are unleashed, they hit the opponent incredibly hard and they cannot be blocked.
Tech Moves are most effective when they are used at the right time. Using a Tech Move when the opponent's power is depleted will likely result in them just blocking it. There are some Tech Moves which begin with an evasive action--try using these moves by timing the evasive portion of the move to first dodge an incoming attack. This will ensure that the latter portion of the move connects cleanly into the opponent. A prime example is the Elbowsmash Combo, but there are also moves which begin with a crouch (like the Tornado Clothesline) and can be used to dodge an upper attack. Note that this may require practice, and should only be attempted by expert players.