What are the visa and immigration methods in the United States?

Visa type 1. There are three kinds of visas: diplomatic visa, official visa and ordinary visa. That is, issuing diplomatic visas to diplomatic passport holders; Official visas are issued to holders of official passports; Ordinary passport issues ordinary visa. 2. According to the entry and exit situation, it can be divided into exit visa, entry visa, entry visa and re-entry visa. For exit visas, only the holder is allowed to leave the country. If you need entry, you need an entry visa. Entry visa: only the holder is allowed to enter the country. If you need to leave the country, you must apply for an exit visa again. The holder of an entry-exit visa may leave or re-enter the country. Multiple entry and exit visas: holders can enter and leave the country within the validity period of the visa. 3. According to the reasons for entry and exit, it is divided into immigrant visa, non-immigrant visa, study visa, tourist visa, work visa, business visa and family visa. 4. According to the length of time, it is divided into long-term visas and short-term visas. The concept of a long-term visa is to stay in the destination country for more than 3 months. It usually takes a long time to apply for a long-term visa, regardless of the purpose of the visit. A visa that stays in the destination country for no more than 3 months is called a short-term visa, and it takes a relatively short time to apply for a short-term visa.