Usually, the various search engines provide their own keyword suggestion tools, which also include the number of searches for each of those keywords. The keyword researcher uses this information to select the correct keyword, depending on the SEO goals of the website. Around 20–25% of searches are very specific long tail keywords entered into Google every single day. It's easy to rank said keywords when there is the right amount of content and backlinks to match. Keyword research is a valuable and high return activity in the search marketing field.
Can't go wrong with the Google Keyword tool, SEMRush and Google Trends. The Keyword tool for volume estimates, SEMRush to see what keywords competitors are ranking for/targeting, and Google Trends to make sure the traffic is actually coming from countries I'm trying to target. Gives a relatively accurate picture of when to expect traffic spikes and seasonality insight.