When issuing temporary visas, every U.S. consular officer begins by making one assumption about the visa applicant: that he or she intends to come to the U.S. to stay. This presumption becomes a problem when someone is applying for a visa that requires the applicant to have "non-immigrant intent" - or the intention to leave the U.S. when they finish their studies, their research, etc. Certain visas - such as the F-1 student and the J-1 exchange visitor visa - cannot be issued if the consular officer believes the applicant will stay in the U.S.
Immigrant intent - the intention to stay in the U.S. - is the number one reason for denials of temporary visas and is often referred to as 214(b) by immigration practitioners and consular officer. 214(b) refers to the section of the Immigration and Nationality Act that describes immigrant intent as a reason for visa denials.