I think G is what you give and P is what you receive. For instance, one of the Warrior's passives allows for improved healing reception, and it's listed as P.
Eden Eternal: Lambda (Lv53/55)
WAR: 30 ~ KNT: 34 ~ TMP: SEALED
THF: 36 ~ M.A: 52 ~ B.D: 46
HNT: 30 ~ ENG: 30 ~ RNG: SEALED
CLR: 40 ~ BRD: 45 ~ SHM: 37
MAG: 37 ~ ILL: 33 ~ WRL: LOCKED