Tags are a great way to highlight key items, organize content, label decisions, and find what you are looking for. Aside from all that, here are how-tos for some of the other ways you can work/interact with tags:
Apply a tag
Within a note, press the pound/hashtag symbol (#) and start typing your tag
Select the tag that you would like to add. If the tag you want doesn't exist, create a new one (see below for more details)
Edit a tag
Hover over the tag that you would like to edit. Click on edit
Edit the content of your tag. Press Save
You also have the option to edit a tag by clicking on the pencil icon next to the tag you want in Workspace Settings.
Star a tag
Hover over the tag that you would like to star. Click on add to home panel then choose the group you'd like to include it in
Once starred, this tag will appear under the category you've select in your home panel
You also have the option to star a tag by clicking on the triple dot menu next to the tag you want in Workspace Settings.
View tagged content
Click on the tag in the note. This will then show you all the content that you have access to where that tag is applied.
Search for that tag directly in the main search panel or search directly in your My Action Items section.
View all Workspace Tags
Click on Tags in the main menu. This will then show you all your workspace tags. Click on the tabs across the top to view your tags or your starred tags.