An ion trap is a device used to capture and hold charged particles, or ions, using electric or magnetic fields. These traps allow scientists to study the properties of ions in a controlled environment, which is essential for various applications in physics and chemistry. One common type of ion trap is the Paul trap, which uses oscillating electric fields to confine ions in three dimensions. Another type is the Penning trap, which combines a magnetic field with an electric field to achieve similar confinement. Ion traps are important tools in fields like quantum computing and mass spectrometry.