The second ring lands features a pressure equalization channel,
  which is a shaped channel that works by equaliztion the pressure
  seen between the top and second ring with the pressure in the
  combustion chamber.
  This feature enhances ring seal, improving power and engine life and
  fuel econony.

  Groove is 1/3 of total lands and 1/3 depth of land and round.

  Top of piston anti-puddling trough.

  Shirt of piston is knurled or grooved.
  Knurling resizes piston bigger and adds pockets for piston and
  cylinder wall extra lube and cooling.
  Grooves collect oil and adds extra lube and cooling to piston and
  cylinder walls.
  Grooves have to be rounded to work right.