Jessie, known as Musashi (ムサシ) in Japan, is a member of Team Rocket, a group of bad guys on the anime Pokémon, and she has red hair - actual red, not orange (although in seasons 5 and up, her hair appears magenta-colored). Specifically, she's in a group also consisting of James and Meowth. Her most notable Pokémon include an Arbok she had to release, along with a Wobbuffet that often pops out of its Pokéball (which she still has), much to the annoyance of Jessie and the others, and a Seviper she caught in the Ruby and Sapphire arc. But, the most important thing to her is her hair. She, along with James, always lose against Ash Ketchum, or in rarer cases, other Pokémon trainers.
Jessie appeared in a few animutations, particulary in the infamous beauty contest screenshot with Misty and James. When she does appear in one, she'll most likely appear with James.
Jessie and James notably made an appearance in Pokémon Yellow.