In simple terms, keywords are ‘search terms’. They are terms that people use to search on the internet. Any website owner that wants to think about SEO must know their keywords. If they do, they can optimize their website to certain keywords, so search engines have an easier time telling what the site and its pages are about. This is essential to drive organic traffic to your website.
Most professionals use paid tools to find out about keywords. There are multiple tools available that will help you with keyword research. They all use different metrics and give slightly different results. What you have to remember is that keywords are created daily. Every day, there is some new phrase that no one has ever searched before.