domain name = business name
If you were starting a restaurant, you would choose a name for your place. If you call it Joe's and put out a sign, no one will know what Joe's is. So, you'll call it Joe's Bar & Grill or whatever most closely describes what you offer so people will stop in. Now, if you are choosing a domain name, it is the same idea. What is your name and what do you do? Try to get those keywords into your domain name so search engines know what you do.