The revenue number a salesperson is expected to close in a period. Their target.
Quotas are set annually (sometimes quarterly), broken into monthly/quarterly chunks, and tracked obsessively. Typical quota is 4-6x the AE's fully-loaded cost, so a $150k/yr AE has a quota around $750k-$1M. Hitting quota triggers variable compensation (bonus + commission); missing it starts a performance conversation.
Quota is the forcing function in sales. It aligns individual effort with company targets. Setting quotas too high demotivates; too low and you're paying bonuses for mediocre performance. Good sales leaders calibrate quotas annually against actual historical data.