are you talking about the keyword competition analyzing tool or keyword suggestion tool? you can check the keyword strength here: type google adwords keyword tool in your address bar
A keyword is a word that is going to be placed in your article several times, not just once as that would make every word a keyword. When a spider sees that you have a word placed several times in an article, it will determine that your page may be useful to users that search for such a keyword.
yes as chinasa said to use google keyword suggestion tool for the selection of keywords.I also use it
Google Ad word is the best tool for analyzing your keywords. And you can also try Keyword-discovery dot com and Hoskinson tool for it.
Google adwords tool, keyword discovery, Word trackers are the ones which you can choose. If you are having confusion over using all at once, pick one. To use them Just type in the search term which you want to target you will be provided with a volume of keywords. So you have to choose from those volumes your choice of keywords. Repeat the same using more relevant keywords and refine your terms. Don't forget to choose the long tail keywords for the best results keeping your short tail keywords for long term gains
Yes, the google one is the best, becuase the searching engine itself is the most important one in the world, and the related tools are very useful for SEOers.
Are the Google Keyword Tool can to collect keywords of your competitors? Can it take into account the sentence on the same topic, but does not include the words you invented? You shouldnt neglect the paid services, such as Semrush ($ 49) Spyfu (79 $) or Keywordspy ($ 89). These tools are more widely implement a keyword search. It is worth it if you're seriously doing your job.
In my mind, I think Google Ad-word and Keyword discovery dot com is the best tool for researching keywords.I always use Google Ad-words for choosing right keywords.But sometimes i use Keyword discovery dot com.