If you’ve never used the Mac’s Console application (Applications > Utilities), this article is a solid place to start. Not only does Kirk McElhearn show off some of the basic Console features, he also focuses on what’s new in the much improved macOS Sierra version.
Console is an important resource. Pretty much everything you do on the Mac ends up sending a message which is accumulated in a log somewhere. Console lets you read through those logs and, as Kirk shows you, this new version of Console makes it much easier to find what you are looking for.
Respectfully, while the new Sierra Console offers some improvements, it comes with an enormous loss of functionality that all but destroys its usefulness for troubleshooting events that have occurred in the past. For many administrators and users, that was the primary reason for using the Console! There are a few good articles on the subject, such as Howard Oakley’s post – https://eclecticlight.co/2016/09/23/sierras-console-promising-but-incomplete/