CHARACTERS HISTORY (taken from Wikipedia):

President Coriolanus Snow:
The main antagonist of the series, President Snow is the autocratic ruler of the Capitol and all of Panem. Though seemingly laid-back, this hides a sadistic and psychopathic mind. He initially appears in The Hunger Games when he crowns Katniss and Peeta as victors, but he doesn't speak to Katniss face-to-face until Catching Fire, when he pays her a visit at home and tells her that he is angry that both she and Peeta were allowed to survive the Hunger Games, as their act of defiance (preferring joint suicide to the prospect of one killing the other) has ignited rebellion in several of the Districts. She is too prominent to kill, but he threatens her family and Gale unless she proves to the Districts that her act of saving Peeta was merely that of a love-crazed teenager and was not related to any desire to defy the Capitol. Later, Snow indicates to her that she failed in this, meaning that some or all of his threats will come true. President Snow is described as having very puffy lips, which are most likely the result of an appearance-altering operation that is very popular in the Capitol. Katniss describes him as exuding a smell of blood and roses. In Mockingjay, it is revealed that the smell of blood is due to mouth sores he got from one of the poisons that he used to kill people in his monomaniacal efforts to control Panem. He drank the poison in order to allay suspicions, then took the antidote, but they could not cure him of the sores. He also smells strongly of genetically enhanced roses. He always wears a white rose in his lapel to cover the scent of blood. The strong smell invariably makes Katniss gag. He is said to have prostituted winning tributes, forcing them to have sex with wealthy Capitol denizens, under threat of killing their loved ones if they refuse. Snow claims he only kills for a purpose and he promises Katniss he will always tell her the truth. Whether these assertions are true or not is left up to interpretation by Katniss. He dies at the end of Mockingjay, but it is uncertain whether he choked to death on his own blood from his untreated mouth sores, or whether he was trampled by a crowd of people.

Commander Paylor:
Originally the head of the troops in District 8, Paylor becomes President two days after Katniss kills Coin.