Giovanni is the Gym leader of Viridian city and is the leader of Team Rocket, he has tried a few times in movies and in normal episodes to take over the world but obviously failed, he almost did in "Mewtwo Returns" but failed in the end, strange that Ash and co. always appear when he is about to suceed.
He appeared quite a few times in the show, including the movies, but mostly not even showing his face.
He didn't exactly lose to Ash because he didn't fight him, but he left Team Rocket; Jessie and James to fight it, they were winning but lost in the end. Many people reckon he is the father of Ash but I seriously doubt it. He has many Pokemon, lots weren't seen battling but a few were seen battling, not used by himself but by Jessie and James, he did battle Gary Oak though. He also owns Pokemon Island, an island full of giant, robotic Pokemon.
These are the people that drive the show along, and appear in nearly every episode!
These are people who appear fairly often, but not all the time.
The gang have made tonnes of friends on their lengthly journey, here are some of the more important ones.
Only appeared once and didn't anything exciting? They'll be here, then!
The Pokemon that stuck around for ages