A perception in the minds of your customers about your company, your products or services, and how they are delivered. For instance, if you asked the man on the street about a Volvo automobile, you would probably end up with a picture of a very safe, reliable, comfortable vehicle, built with superior engineering, which justifies a higher price. Whether this is true or not is moot. The fact is that this notion was carefully crafted by Volvo, and it's marketing and advertising agencies.
The fact is, from the moment you open your doors, you will be building your brand. Everything your potential customer sees and hears will influence his opinion about your business. What your potential customers think about your business, true or not, will influence your brand. Does your brand engender trust in your customers, establish value in your products and services, give the impression that you will stand behind what you sell? Or not?
Keep in mind that the first point of contact with your customer will usually be through your website, advertising, or your storefront. Through these media, you are offering your customer a peek inside your business. Take a few minutes and put your self in your customer's shoes. Try to see your business through his eyes:
Does your place of business give the impression that you have been, and are going to be be around for a while? Clean, businesslike, appropriate signage, etc.?
These are just a few of the things that help determine your brand. Carefully designed branding will attract new customers, retain old ones, and help you to focus your business on what is most important.