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.
Flat top pistons are very similar in nature to stock pistons, running at medium compression ratios. Consequently, they work great in many applications and performance levels. Valve reliefs are designed with appropriate clearance to fit most types of standard and aftermarket heads.
A Solid Dome top piston will effectively raise an engine's compression ratio, making them the ideal type of piston for medium to higher performance engines that may be using power adders (such as nitrous). Dome Top pistons range from medium to high compression ratios.
Hollow Dome pistons are designed specifically for applications where race fuel and nitrous are the norm. They are typically used to make motors with high compression ratios and high performance combinations only.