The TIP120 is a NPN Darlington Power Transistor. It can switch loads upto 60V with a peak current of 8A and continuous current of 5A. This makes it suitable for medium and high power electronics like controlling motors, solenoids or high power LEDs.
2N3055 is a general purpose NPN power transistor manufactured with the epitaxial base process, mounted in a hermetically sealed metal case. The device is designed for general purpose switching and amplifier applications.