The customer-facing contract that promises a level of service, typically with financial credits for breaches, the legal twin of the SLO.
A Service Level Agreement (SLA) is a customer-facing contract that commits to a level of service, typically uptime ('99.9% monthly availability'), response time ('p99 under 500ms'), or support response ('Sev-1 acknowledged within 15 minutes'). Breaches usually trigger service credits. SLAs are typically less strict than internal SLOs by one nine, so the team has buffer to miss the SLO without breaching the SLA.
Engineering tracks SLOs internally; sales and procurement talk SLAs externally. The two need to be related (the SLA derives from the SLO with a buffer) but they're not the same. Most disasters happen when the team commits to an SLA they can't actually hit because there's no internal SLO discipline to drive the engineering investment.
See the part of the platform that handles sla (service level agreement) in production.