You can use Keyword Planner to identify:
the number of negative keywords you should add
the amount of traffic potential keywords might get
which text ads are performing best based on your keywords
webpages where your ad can appear based on your keywords
Keyword Planner is a free AdWords tool for new or experienced advertisers that’s like a workshop for building new Search Network campaigns or expanding existing ones. You can search for keyword and ad group ideas, see how a list of keywords might perform, and even create a new keyword list by multiplying several lists of keywords together. Keyword Planner can also help you choose competitive bids and budgets to use with your campaigns.
A tool that provides keyword ideas and traffic estimates to help you build a Search Network campaign.
Read more here: https://support.google.com/adwords/answer/3114286?hl=en