Microsoft has a straightforward definition and it includes DLP. "is a security policy enforcement point positioned between enterprise users and cloud service providers" https://www.microsoft.com/en-us/security/business/security-101/what-is-a-cloud-access-security-broker-casb A cloud access security broker (CASB) works by securing data flowing to and from in-house IT architectures and cloud vendor environments using an organization's security policies. CASBs protect enterprise systems against cyberattacks through malware prevention and provide data security through encryption, making data streams unreadable to outside parties. CASBs were created with one thing in mind: protecting proprietary data stored in external, third-party media. CASBs deliver capabilities not generally available in traditional controls such as secure web gateways (SWGs) and enterprise firewalls. CASBs provide policy and governance concurrently across multiple cloud services and provide granular visibility into and control over user activities. https://www.forcepoint.com/cyber-edu/casb-cloud-access-security-broker

Explanation
The total loss expected per year due to a threat targeting an asset can be calculated using the Single Loss Expectancy (SLE) multiplied by the Annualized Rate of Occurrence (ARO). SLE is the monetary loss expected from a single event, while ARO is the estimated frequency of that event occurring in a year.
Reference: CompTIA Security+ Study Guide: Exam SY0-501, 7th Edition, by Emmett Dulaney and Chuck Easttom, Chapter 9: Risk Management, page 414.