Geo has explained it well, but I'll just add this - to remove the tack from the tape, the easiest and most sure method is to cut the length you require, and then pull it lightly between finger and thumb two to three times. This removes the 'top layer' of tack evenly along the length of the tape.
When removing the tape, lift a corner or edge, and then gently pull the tape away along its length, keeping the 'free' end at around 45 degrees.