Two classes of visas are processed by U.S. Consulates abroad: immigrant and non-immigrant.
To qualify for permanent residence, an applicant must have or be one of the following:
A personal interview for permanent residence is normally required before a U.S. Consul who will examine eligibility as well as confirming that the applicant is not inadmissible for an aggravated felony, a prior order of deportation, for public health reasons, or for suspected terrorism.
Admissions on a temporary basis are usually referred to by letters and numerals such as B-2 (tourists), E-1 and E-2 (treaty traders and treaty investors), F-1 (students), H-1B (temporary professionals), J-1 (cultural exchange visitors), K-1 (fiance’s of citizens), L-1 (intra-company transferees), etc. These non-immigrants must satisfy a Consul that they wish to enter the U.S. for a limited time and for a specific purpose. All non-immigrant applicants except (H-1) workers, intracompany transferees (L-1) and (V) family members must show that they are not coming to live here permanently.
Usually, personal interviews are required.