Welcome to TV
RL = regular leaf. PL = potato leaf. grow out: growing many seeds of a particular variety to get a "seed crop" or when developing a new variety, growing many seeds to get all the genetic variations so you may keep the traits you like and weed out the rest. this is done over many generations.
im new too but if you cant find it here you cant find it anywhere.
many here know much more so i will get out of the way.
best of luck
dave