Although the piston is an integral component, it is divided into three structural areas with different functions to complete complex tasks: the head, skirt, and pin seat.

　　Piston head: including piston crown and ring groove. The shape of the piston crown depends on the design of the combustion chamber: gasoline engines are mostly flat topped to reduce the heating area and distribute stress evenly; Direct injection diesel engines, on the other hand, have pits of varying depths on the top to create vortices and promote the formation of the mixture. The ring groove is the position for installing piston rings, usually with 2-3 grooves, used for installing gas rings and oil rings.

　　Piston skirt: refers to the lower part of the piston, which guides the piston to reciprocate in the cylinder and withstand lateral pressure. Due to uneven radial expansion of the piston after heating, modern piston skirts are often designed in a "convex to elliptical" shape, which is not a cylindrical shape at room temperature, to ensure that they can adhere to the cylinder wall after being heated.

　　Piston pin seat: located above the skirt, used to install the piston pin connecting rod. In order to reduce engine noise, the center of the pin hole in many high-speed engines does not completely coincide with the centerline of the piston, but is offset to one side by a certain distance (usually biased towards the main thrust surface). This offset design can make the piston transition smoother when changing the direction of motion at the top dead center, significantly reducing the knocking sound.

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