The stylus is the part of the record player that comes into direct contact with the upward-facing side of the album as it spins. A record player’s stylus is actually a tiny piece of unrefined diamond that is cut into a specific shape. This little piece of diamond is housed in your turntable’s cartridge. The stylus picks up specific frequencies from the grooves etched into a vinyl record, vibrating at these frequencies and transferring the vibrations to the other components in the cartridge.

Source: The Sound of Vinyl