While the Pyroar's share of mysteries in the world of Pokemon pertains to the nature of Pokemon themselves, a different kind of mystery has been lingering since the series' beginning. Team Rocket's pursuit of Pikachu, a tale as old as the anime itself, has only ever been an attempt to impress one man. Despite being the leader of Team Rocket and having made numerous appearances throughout Pokemon, very little is actually known about Giovanni.
The former Viridian City Gym Leader, Giovanni's primary concern is his criminal organization known as Team Rocket. Tasking his grunts with stealing powerful Pokemon, the goal of this crime syndicate is to use Pokemon to grab power or sell them for a high profit. Though he seems to treat his Persian with genuine affection, Giovanni considers all other Pokemon to be no more than a means to his own ends. But what else has Pokemon told viewers about him?
Next to nothing is known about Giovanni's past -- the only real tidbit of information comes from a radio drama called The Birth of Mewtwo. The program was originally broadcast exclusively in Japan during the weeks leading up to the release of Mewtwo Strikes Back in June of 1998. In the drama, it's revealed that Giovanni's mother was the leader of Team Rocket before he took over.
Known only as "Madame Boss," she is the true founder of Team Rocket, having passed her rank down to her son. Giovanni is said to hold his mother in high regard and likely learned his brutal ideologies from her. Though his mother did not think very highly of him, she left her criminal enterprise in his hands nonetheless. It's unclear if The Birth of Mewtwo is meant to be canon in the Pokemon anime, but it's the closest thing to an origin story Giovanni has ever received.
Pokemon the Series: Sun & Moon reveals that Giovanni has a personal relationship with Nanu, the Kahuna of Ula'ula Island in the Alola Region. While seeking information on a Legendary Pokemon, Giovanni was surprised to hear Nanu had become a police officer. The extent of their past relationship is unknown, but Giovanni's willingness to seek answers from him indicates it may have been something resembling a friendship.
The only other extended character interaction Giovanni ever has is with Jessie, James, and Meowth. Sometimes he needs to be reminded who they are, other times he chastises them, and occasionally he places his utmost faith in them. He even chose them to be by his side when he attempted to conquer the Unova Region during his most active participation in Team Rocket's endeavors. During this plan, he was shown to be an adept battler as his Persian was able to defeat Ash's Pikachu.
Giovanni's skill in battle may indicate that he once held a legitimate desire to become a Pokemon Trainer, which would explain his former status as a Gym Leader. It never made much sense that he led a Gym in the context of his villainous behavior, as the sole purpose of Pokemon Gyms is to help trainers. A Gym that was stealing Pokemon would have been noticed very quickly, so his time there didn't appear to serve any purpose for his criminal ambitions.
However, his cruel and sometimes outright evil behavior seems to be the truest indication of his character. Other than Persian, Giovanni keeps his Pokemon in cages when he has no need for them. His general disdain for most Pokemon even clouds his judgment. If he had simply told Mewtwo what it wanted to hear when it confronted him about their partnership, it likely would have remained loyal to him. Instead, he belittled the clone, which led to its escape and subsequent attempt at world domination.
There doesn't appear to be much of a path forward for Team Rocket's criminal overlord. Each time Giovanni takes an active role in the Pokemon anime, little about him is revealed and he doesn't learn any lessons from his failures. Unfortunately, Team Rocket's pursuit of Ash's Pikachu only sustains itself with the threat of Giovanni looming over Jessie, James, and Meowth. As long as the trio remains in their current roles, Giovanni will be forced to remain in Meowth's nonsensical fantasies.