What is FB1

fb represents the inductor component. fb1 was probably discovered by the original poster when he was looking at the pcb board. The inductor is labeled 1

More accurately, it should be called a magnetic bead. See the quotation below for details.

A coil with more than one turn is customarily called an inductor coil, and a coil with less than one turn (the wire goes straight through the magnetic ring) The coils are usually called magnetic beads. It can be said with certainty that FB (generally called magnetic beads) is also an inductor, but the inductance is relatively small! Roughly speaking, inductors are energy storage components, while magnetic beads are energy conversion (consumption) devices. Inductors are mostly used in power supply circuits, and are generally composed of filter circuits with other components to improve power quality. Widely used in high frequency circuits! As for the actual function, you can refer to some books related to electronic basics and power circuits!