For example, suppose we want to do a blog about shoes. In that case, we introduce the term "shoes" in the search box and select a country and language.
Then we will get a list of words and phrases that have to do with our search term. The first corresponds to our criteria exact search (shoes) while the rest are similar phrases with corresponding data, so you can get an idea of how many searches have and the number of companies "compete" to put their ads on pages that address these issues.
In "shoes" we see a medium level of competition, with more than 6 million global searches per month, of which more than 2 million are in the local site (in this case had selected United states, but we can change from country to go see how the number).
However, the word "shoes" is very general, so we can take a look at the results related and observe that phrases like "buy shoes online", "online sales shoes" or "shoes large sizes" are well paid by advertisers and therefore, we would make more money if their banners appear on our page. The number of monthly searches, however, is much smaller, so there will be fewer people looking for this type of information.
The ideal is to find keywords with high competition and many searches monthly.i hope you now you ready to rock with google keyword tool cost per click.