There are several things which must be considered demographically in order to clearly define the target audience.
Sex, age, ethnic background: This information is essential and in this case would be provided by the target audience of the product itself. Sometimes ethnic background is not an important consideration; but, as colors and terminology have different meanings from country to country, it is important to know so designers can prevent the site from evoking the wrong emotion and foster usability.
Marital Status: The importance of this information will vary from project to project, however, in the case of the computer gadget will be beneficial in the sense that it may be something better suited for a single person, or a married couple.
Occupation and Income: In the case of the computer gadget, occupation and income are very important, depending on what the gadget actually is. For instance, office professionals will likely be a huge portion of the target audience, though if the product is expensive, the target audience goes from office professionals to office professionals who earn more than $100,000 annually.
Geographic Location: Not always important, sometimes where a user lives and conducts his or her work is important to the overall design of a website. Because the computer gadget will likely be marketed nationwide, it is not a major detail, though it still should be considered when choosing hours for customer service, order and shipping cut off times. Knowing where the audience lives will allow for a time frame everyone can use once again fostering usability and appealing to the audience on the basis of convenience.
Technological Expertise: Depending on exactly how highly technological this computer gadget is, some people may not have the knowledge to use it. Targeting members without the necessary expertise is a waste of time. If someone comes to the site looking for this gadget, he or she is likely technologically advanced enough to make use of it.