A solenoid can be a thin wire looped, or wrapped, around a metallic object. When electricity is passed through the wire, a magnetic field is generated. A solenoid can also be a transducer that converts energy in linear motion. It can be used as a switch to turn something on or off.
Computer motherboards contain solenoids and perform various functions. One important function is to help regulate the power coming from the power supply, to minimize the chance of voltage spikes and motherboard damage.