What is the difference between R20 and PAR20 lightbulbs?
According to this site: 


  R20 bulbs have reflectors that direct light forward and produce more narrow soft-edged beam that is less precise than PAR20 bulbs. R20 bulbs also produce less shadow than PAR20 bulbs. PAR20 bulbs control light more precisely and produce more concentrated light than R20.






Source: http://www.agreensupply.com/difference-between-par20-and-r20-led-light-bulbs/