Don't make the common mistake of thinking that 'everyone' is a prospect for your product or service. You'll go broke pretty quickly trying to reach everybody.
People are looking for products and services that appeal to their specific needs. The more closely you align your product or service to the specific needs of a particular group of prospects, the more you will sell, and the more loyal your resulting customers will be.
A specific group of prospects who share common likes, needs and desires is called a Niche Market.
For an easy example, think of music. There are musicians who appeal to the rock and roll niche, heavy metal niche, easy listening niche, country niche, country rock niche, jazz niche, classical niche, etc.
Here are some more examples:
A marketing consultant could focus on the church niche, or the chiropractic niche, or the dentist niche, or the fitness niche, etc.
A builder could focus on the low-price home niche, or the medium-priced home niche, or the high-priced home niche.
Keep in mind that when you select your niche that you must have an easy way to reach the prospects in that chosen niche. There's no benefit to you to have a huge niche of prospects that you can't reach with your marketing messages.