In tennis, the “sweet spot” is the spot on the racket that has the greatest bounce to it.
Internet Marketing has its “sweet spots” as well.
There may be a lot of search terms which relate to your products or services.
Some of these may have hundreds or thousands of times as many searches as others. For example, in hardwood flooring, searches for “Armstrong Floors” as opposed to a small, lesser known brand.
BUT some terms which get a lot of searches may be not be relevant to your business. Something like 99% of all searches for “Amstrong floors” are NOT for hardwood but for tile or other Armstrong products.
This combination of search volume and relevance determines the value of a search term to you.
Finally, the amount of competition for some valuable terms may be intense, to a point where getting high search engine rankings is very difficult. This isn’t true in every industry and situation by any means. It’s far more common where you are fighting over national rankings than when you are selling local goods or services.
What we call the “sweet spot” consists of the search terms with the most volume and relevance with the least amount of competition.
This is why research should be a part of every search engine project. Otherwise you can end up with #1 rankings for search terms that result in no visits or no sales.
That, after all, is why you are trying to get high rankings in the first place.