USA B2 visa is issued to the tourists who want to visit USA. There are certain eligibility factors which are considered for you to get the B2 Visa. You can get the application for free in any US government site. Once you have submitted your application your application is validated and checked thoroughly by a counsel who will decide if you can or cannot get a visa. There are several reasons why your visa gets rejected. Most common belief of applicants for the visa getting rejected is that the counsel was not convinced of your purpose of visit to USA. This stands true only in some cases. In most of the cases the rejection is based only under two sections. Sections 221g or 214b of the US Immigration and Nationality ACT your application is refused.
If your application is rejected in this particular section then it means that you have incomplete documentation with you. If you can bring along the complete documentation and resubmit it to the counsel then there is a chance of evaluation. In some cases even due to additional information required, your visa application may be rejected.
If your application is rejected under this section then that means you do not qualify for B2 visa. The reasons may be different for your non-qualification. Also if the counsel feels that your purpose of visit is not suiting your profile. It may be understood that you are applying for this visa to illegally work in USA. When your application is rejected in this section you need to fill a new application all together once again. Whenever you go for your visa interview if your visa gets rejected you can ask for the reason why you are getting rejected.