Playing guitar with a pick produces a bright sound compared with the fingertip. Picks offer a greater contrast in tone across different plucking locations. Brightness between plucking close to the bridge and close to the neck is much greater when using a pick compared to a fingertip.
Guitar picks vary to accommodate different playing styles and kinds of strings. Thinner plectra are more flexible and tend to offer a wider range of sounds, from soft to loud. Probably the most famous and easily recognizable name on a pick is the logo of Fender Guitars. Custom picks have become more popular over the last few decades. That is rare to find a famous artist who doesn't use a custom pick.