Misty is a fictional character, a redheaded, 12-13 year old girl who appears in several seasons of the american Pokémon dub. She wears a yellow tanktop and short shorts with suspenders. Filling out the female audience identification quotient of the show, she likes many typical 'girl' things but is somewhat of a tomboy (and thus has a small complex about herself, especially due to her pretty but annoying 3 sisters). Although usually the most calm and sensible one, she can be stubborn and temperamental, especially around stupid people. She reins in Brock when he gets overamorous with cute girls. She is also afraid of bugs.
Misty wants to be a world-class water Pokémon trainer, and her Pokémon are appropriate to such. She meets Ash after he borrows/steals her bike and wrecks it. She eventually leaves in the Pokemon Advanced season.
Misty's original Japanese name is Kasumi, which can refer to air or indeed mist.
Although it has been used for potential humor, Misty/Kasumi has never shown canon romantic feelings for Ash/Satoshi.