Acoustic guitar pickups sit in and around the body of your instrument. There are three main types. Magnetic pickups sit in your soundhole and track the magnetic field of your strings. They have a warm, detailed tone that works well with pedals and can be compared to an electric guitar.
Piezo pickups attach underneath your bridge and detect the vibrations of the soundboard. They have an articulate and somewhat brittle tone. Internal microphones capture the natural acoustic sound of your guitar as if you were in a studio. They pair very well with piezos as each excels at picking up different frequencies.