What does the starter do on a 3 phase motor?

So Was looking at the 3 phase motor of the table saw in my school shop. To one side separate from the motor is a small box labeled the "starter". I am confused because I thought that 3 phase motors were self starting because of the angle between each phase. So what is the purpose of the starter?
Update: Also, what does the starter consist of? Is it a set of capacitors?
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