Screen shot by J Kyrnin
The term "internet safety" doesn't get a lot of searches - only 5419. I can optimize for that phrase, but there might be one that gets more searches.
There are two schools of thought when it comes to SEO:
Optimize for the Most Searched Terms
This is where you are just trying to get a slice of the pie. And if the pie is really big (in other words, lots of searches for the term) even if you only get a small percentage of the pageviews, you're going to get a lot.
Terms with a large number of searches can get very competitive. Chances are, if you're thinking of optimizing on that term, then so are hundreds or thousands of other people.
Get to Number 1 For a Smaller Term
This is where you work on getting your page to the number 1 slot for a term with a smaller number of searches. In this case, if I optimized for "Internet safety" I would want to get at least to the top 10 of search engines for the term. That way I would capture a large share of a small number of searches.
This method isn't as competitive, but there isn't as much to get.