In one sentence, SLO is part of SLA. SLA is a legal contract while SLO has some specific definitions regarding performance, which can be used to guide performance testings.This topic is actually well discussed in the links below: - [Differences between SLA and SLO][1] - [SLA and SLO discussion on Quora][2] - [SLA on Wikipedia][3] - [SLO on Wikipedia][4] [1]: http://searchcio.techtarget.com/answer/Whats-the-difference-between-SLO-and-SLA [2]: https://www.quora.com/Whats-the-difference-between-Service-Level-Agreement-SLA-and-Service-Level-Objective-SLO-in-the-IT-industry [3]: https://en.wikipedia.org/wiki/Service-level_agreement [4]: https://en.wikipedia.org/wiki/Service_level_objective