The Data Loss Prevention scheme works with DLP policies to scan a text field for sensitive content, and encrypt the content only if there is a match.
For example, for your Salesforce or ServiceNow service, you could have a comments field. For that field, you would select Data Loss Prevention encryption. In your DLP policy, you would create a proxy rule to configure what sensitive content you're looking for in the comments field, and set the policy action as "encrypt".
Use Case: For example, you can scan for sensitive content in a Salesforce Chatter post, or in a ServiceNow Live Connect post, and encrypt the content only if there's a match, according to your DLP policy.