What’s the difference between Copy all, Copy unused keywords, Copy unused single words?

Let's assume your project has these 3 keywords.

The third keyword (keywordC) as well as a partial of your first keyword (keywordA2) are used in your project.

Copy all will copy everything. Great if you want to make a backup of your keywords or copy all your keywords to use elsewhere. Your copied keywords should look like this:

keywordA1 keywordA2
keywordD
keywordC

Copy unused keywords will copy all the exact match keywords that are not used in your project. Your copied keywords should look like this:

keywordA1 keywordA2
keywordD

Copy unused single words will copy all the single words that are not used in your project. Great if you want to copy the words you didn't get to use to your backend search terms. Your copied keywords should look like this:

keywordA1
keywordD