Jessie and James, along with Meowth, make the main antagonists for the show, Team Rocket. There trio is introduced as competent villains, but as the story progress, they become desparate as the rest of Team Rocket abandons them. They become poor, but devoted to catching Pikachu. Jessie Joined Team Rocket after her mother, who died investigating the mysterious pokémon Mew. For most of her life, she had to live in an orphange without a mom, and grew up so poor she would pretend to eat snow cones by using real snow. Team Rocket not only became her job out of legacy for her mother, but out of desparation for a job, being of no use in any other job. James on the other hand grew up in a wealthy family, but one that treated him poorly. Forcing him into an arranged marriage with an abusive bride at such an early age, James ran away from home, with his parents abandoning him for not following their values. James, leaving his life at such an early age, had no choice but to join Team Rocket for a living.
Finally, Meowth is a talking pokémon that thinks of itself as a human, equal to Jessie and James. Living on the streets his whole life, he wanted to impress Meowsy, a female meowth, by acting as a human as Meowsy only cared to be pampered by her human owner and only valued other humans with her time. However, after teaching himself to walk, talk, and behave like a human for her, Meowsy rejected him for being a low class freak. Meowth's ability to talk made him a rarity, spoiled by the boss of Team Rocket, Giovanni, until realizing that Meowth's knowledge of being a human made it forget any of its pokémon capabilities, making him, yet again, a low class freak, and found himself working with Jessie and James who respect him as an equal.
The ruthless boss of Team Rocket, Giovanni, did not start out his life as the evil criminal mastermind he is now. He was a trainer just like Ash that became corrupt, selling pokémon as a business. His mother was the original boss of Team Rocket, and treated him poorly, telling him that money is more important than anything. Giovanni eventually quit his journey to become a Pokémon Master and started to work in crime. Eventually taking over Team Rocket, he became a mob boss that worked in stealing and trafficking pokémon to others. He eventually funded in research for a project in cloning the powerful pokémon, Mew.
The Pokémon franchise belongs to Game Freak and the Pokémon Company. You may watch the original series on Netflix