Keyword planner can serve you in all respects, except suggesting a keyword that never happened to you before.
Keyword planner can quantify the quality and validity of keywords, based on historical data; it can provide statistical analysis of keyword’s strength.
Keyword Planner is a free AdWords tool for the beginner and polished advertisers, just like a workshop for designing a new search network campaign or polishing an already one. This can also assist in figuring out the value of bid and estimating the budget of your chosen campaign. You can search for any keyword or ad group idea, explore its performance and even create a new one by shuffling or rearranging the already existing keywords.
Read more here: https://support.google.com/adwords/answer/2999770
