What is the difference between Must Have attributes and Keywords?

What is the difference between Must Have skills and the Keywords section?

1. Must have skills look for mention of the skill in Github repos, Skills, candidate Bios and job descriptions.

2. Keywords look everywhere in the enriched profile.

Is one better to use than the other?

That depends. If pure volume is what you’re after, use keywords. 

If the skill you're looking for is also a common word, use must-haves; this is because with keywords, you might get other unrelated profiles (i.e., JAVA must-have skill returns 7 million profiles, whereas JAVA keyword returns 12 million.

When would a user need to use keywords OVER must-have skills? Or both?

In general it’s fine to use keywords unless there’s some reason you would need to specifically look in Github repos, skills, candidate's bio or job description.