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I saw a need for a demo of logic driving a relatively high-current device, so here it is.
The two transistors make a Darlington pair. This has very high gain, letting the low-current logic drive the high-current motor. They are different, a small high-gain transistor drives a large, low-gain transistor which can handle a high current.
A separate power supply provides the high current the motor needs. EC has perfect power supplies, but a less perfect power supply would show dips and spikes when the motor starts and stops -- noise which should be kept away from the sensitive logic circuits.
The diode doesn't seem to be needed here, but is normally recommended with inductive loads such as motors, relays, and solenoids. It really is needed with relays and solenoids.
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