Inductor vs a capacitor
To answer this properly, you should know the properties of a capacitor and an inductor.

Inductors are one of the primary components required by a switching regulator. A capacitor and an inductor are similar in the way that a capacitor resists a change of a voltage and an inductor resists a change in current. The "strength" of their resistance depends on their value

Capacitors are widely used to clean up a power supply line, i.e. remove noise or ripple at (higher) frequencies. Inductors are used in switching power supplies where a relatively constant current is passed through an inductor. 
A switching power supply works in that a switch is opened and closed very quickly. When the switch is closed, the inductor is 'charged'. When the switch is open, the energy is drawn from the inductor into the load. Usually such a power supply is being decoupled with a capacitor to create a stable power supply line.

An inductor is required to make this principle work. If you know a resistor that has an equal resistance for all frequencies of signal, you should view a capacitor as a resistor that will be infinite for DC (0Hz) and 0 for high frequencies. An inductor will be the opposite: it's resistance will be 0 at 0Hz, and infinite at high frequencies. However we don't call this resistance (that's only used for a pure resistor!) but impedance.

A PC motherboard or graphics card is basically not much else than this. They have their main chips and the routing between them, and most other components are power supply or a little bit of interfacing between chips or connectors.