Magnetic beads are used to suppress high-frequency noise and interference on PCB boards, absorb electrostatic pulses, eliminate RF noise in transmission line structures, and are commonly added to circuits like RF circuits, PLLs, and memory circuits. They help filter out AC signals while allowing DC signals to pass through, provide high impedance in the RF noise frequency range, and must be selected based on factors like frequency range, noise source, noise attenuation, environmental conditions, and circuit impedance. Chip inductors are necessary in resonant circuits, while chip beads are preferred for eliminating unwanted EMI noise in various applications.