This statement is correct: Magnetic fields exert a force on all moving electrically charged particles.
A particle with the charge q and velocity `vecV` placed in the Magnetic field `vecB`
will experence the force known as Lorentz force:
`vecF = q* vecV xx vecB` (this is a vector product of the magnetic filed and particle velocity vectors)
This force is perpendicular to both velocity of the particle and the magnetic field. Its magnitude is determine by the particle's charge and speed and the strength of the magnetic field:
`F=qVBsin(alpha)` , where `alpha` is the angle between the velocity of the particle and th field line.
Please see the reference for more information on how to determine the direction of this force and what kind of motion of the particle will result.