Interpretation.. What you are asking is so generic. You need to investigate the logs and interpret them based on cases.. Case by case..
If you have clues, you will dig deeper for the interpretation..
For instance -> How to Interpret Node Manager [deleteOldFiles] Log Entries (Doc ID 2561309.1)
Some note for the reference:
Primary Note on Oracle WebLogic Server Debugging Capabilities and Resulting Output (Doc ID 1299766.1)
Oracle Fusion Middleware Administering Oracle Fusion Middleware 12c (12.1.2) ->
https://docs.oracle.com/middleware/1212/core/ASADM.pdfhttps://docs.oracle.com/cd/E28280_01/core.1111/e10105.pdf -> Oracle Fusion Middleware Administrator's Guide 11g Release 1 (11.1.1.7)
Following Youtube video offers a visual guide on locating and understanding WebLogic server log files, including managed servers and the Node Manager -> "Weblogic Server and Node Manager Log Files, View, Change Name, Parameters and Rotation" -
https://www.youtube.com/watch?v=vKu0CEntB_8