Dishwasher tablets go directly into the main detergent slot on the dishwasher door, and as the cycle progresses, the door releases the tablet into the water with the dishes. The tablets then dissolve to provide the cleaning action for the dishes.
Some brands, such as Cascade, come with dishwasher tablets shrinkwrapped in plastic. These go directly into the detergent slot, and the hot water dissolves the plastic as well as the soap. Other brands, such as Finish, package tablets in individual wrappers that the user must remove and discard before putting the tablet into the detergent dispenser. In both cases, the manufacturers have chosen an amount of soap to use for each load, keeping the user from having to guess how much to scoop into the dispenser.
Some tablets come with a rinse aid and water softeners in addition to the detergent, while others combine soap and an emulsifying agent to remove grease. Different brands and varieties market different traits. For example, the Dawn ActionPacs are designed to help certain varieties of Cascade dishwasher tablets eliminate greasy residue from dishes without having to add an additional cycle. Some brands of dishwasher tablets, such as those made by Cascade, come in a variety of scents.