A Dish Top style piston will effectively lower your engine's compression ratio by removing material from the top of the piston in a circular, "dish" shape. They are primarily used in boosted (supercharged, turbocharged) applications where low to medium compression ratios are desired.
Similar to a dish piston, the goal of a Reverse Dome piston is to lower the compression ratio of your engine, making them great for boosted (supercharged, turbocharged) applications. They are designed in such a way as to match the profile and shape of most standard and aftermarket cylinder heads.