[AGNTLOG-229 Multiline features FAQ

content/en/agent/logs/advanced_log_collection.md

@@ -715,6 +715,21 @@
 
 **Note**: The Datadog Agent does not start the log collector if there is a format issue in the global processing rules. Run the Agent's [status subcommand][6] to troubleshoot any issues.
 
+## Multi-line log aggregation FAQ
+
+**1. When should I use manual multi-line rules vs. automatic multi-line detection?**
+
+If you know the format of your logs, you should use manual multi-line rules for precise control. 
+If you are sending lots of multi-line logs, and you are unsure of their format or don't have the means to configure all sources individually, you should use automatic multi-line detection.
+
+**2. What happens when a multi-line pattern doesn't match any logs?**
+
+All non-JSON log lines are processed individually as separate log entries.
+All JSON-formatted log lines are treated as a single line of logs, and only the first valid JSON format enters the intake; the rest are dropped.
+
+**3. What happens when there are both global rules and integration-specific rules?**
+Integration-specific rules completely override global rules for the particular integration.
+
 ## Further Reading
 
 {{< partial name="whats-next/whats-next.html" >}}