Long-tail keywords are search phrases, rather than one or two words. If you are planning to promote an online poker course for example, you might do some keyword research and decide that the term "online poker course" has too much competition from existing websites, but articles based on things like "When to push during a sit-n-go" don't have as much competition and may yield more traffic.
It can take time to build up your personal freelance business. Yet, there is more demand than ever for freelancers. So, if you want to kick start making money online through freelancing you can join one of the top freelance networks, such as Flexjobs, SolidGigs, Contena, Upwork, Fiverr, or PeoplePerHour. Sign up, build your profile, upload some samples of your work and start making extra money by doing small freelance jobs.