Broad match searches are the default setting in the keyword tool, and unfortunately the least useful because they return a highly inflated number. If you are searching for "Niche Site" the broad search will return the number of searches containing "niche," "site," "niche site" or any other word that Google deems related in any way. Needless to say, this could lead you to believe you have found a niche that has a lot of searches and huge traffic when in reality it could be the opposite.

Phrase Match:

Though the phrase match is a bit broader than exact match, it is still useful. Once again let’s assume your researching the keywords "niche site." The phrase match will return the number of searches that include ALL the words in your search, but may have variations. This will, for example, include searches for "super niche site" , "niche site central" or "niche directory site."

Exact Match:

This is by far the most useful metric out of the three. This provides you the number of monthly searches for your EXACT keyword: "niche site"  …no variation or additions. When picking keywords to focus on this will give you the most unadulterated data.