Non-immigrant visas allow people who are not US citizens or permanent residents to enter the US for a limited period of time, which varies from anywhere between 90 days to ten years. It is best to always check the conditions of the visa granted, as they are not all the same. A non-immigrant visas implies that the person carrying it has no intention of staying in the US on a permanent basis.
There are a variety of non-immigrant visas, but the most common issued are for visitors who want to get medical treatment, study, work on a temporary basis, carry on business or tour and shop. Some non-immigrant these allow repeat entries into the country, while others are only good for one trip.
Waiting periods vary, largely because the US government has substantially changed its national security measures. This makes any review process longer and more involved. If traveling to the US, apply for a visa early. To apply, certain items are required, such as application fees, supporting documents, photos and a passport. Once a visa has been issued, it must be shown to customs officers at the border. Having a visa is not an automatic guarantee that an individual will be allowed to enter the US. This decision is made at the border.