RPO is the total dollar amount of contracted future revenue that hasn't been recognized yet - multi-year contracts where the company has booked the deal but the service hasn't been delivered. Disclosed quarterly by public SaaS. Often broken out as cRPO (current = next 12 months) and long-term RPO (>12 months). Higher RPO relative to ARR = stronger renewal visibility.
See how public B2B SaaS companies disclose this metric, with full historical time series.