Phrase search is when the keyword is surrounded by quotes "keyword example". The two keywords must be together such as "big keyword example" or "keyword example number two". But it can't be "keyword bad example".

I'm coming from the keyword research perspective. If a keyword has a search volume (exact) of say 20,000 and the search volume for broad match is only 500 is that keyword still as attractive (purely from an seo traffic perspective). Which do you focus on the broad or exact match?

My question seems basic in nature but some recent keyword research has caused me to re-think broad vs. exact match.

I was taught to focus on exact match for the short term and broad match for the long term prospects of a keyword. Today I was researching a niche of keyword phrases where the local search volume (broad) was, for example 33,000. The local search volume (exact) was only 500. What I know about broad vs. exact doesn't help me to determine if this keyword is worth going after. The keyword difficulty score by the way was 35%

Yes, I do know that I will probably go after this keyword anyway but to refine my question, how do I get an idea of how "big" this keyword is? Is it more on the broad or more on the exact match of things? How do I determine the various derivatives of the phrase that occur under the broad match?