H-4签证是美国的一种非移民家属签证类别，专门为H签证持有人的配偶和未满21岁的未婚子女设计。H-4签证持有人可以随同主申请人的H签证一同来到美国，并在主申请人的授权逗留期间在美国居住。以下是H-4签证的详细解释：

  1. 资格条件： H-4签证的资格取决于主要H签证持有人的身份。要符合H-4签证的资格，申请人必须是H-1B、H-2A、H-2B、H-3或H-1B1签证持有人的配偶或未满21岁的未婚子女。
  2. 陪伴家属地位： H-4签证持有人被视为主要H签证持有人的“家属”。作为家属，他们在美国不允许工作，除非他们自行符合其他途径获得工作签证或就业授权的资格。
  3. 逗留期限： H-4签证的有效期取决于主要H签证持有人的签证有效期。H-4签证持有人可以在主要H签证持有人维持其身份且停留在美国的期间内居住。
  4. 学习： H-4签证持有人允许在美国学习。他们可以在学校、学院、大学或其他教育机构注册，无需获得单独的学生签证。
  5. 出行： H-4签证持有人可以在其签证有效期内出入美国。但如果打算在国外旅行，他们需要确保签证仍然有效以便重新入境。
  6. 状态变更： 如果主要H签证持有人改变其签证状态或调整到其他移民状态，H-4家属可能也需要申请状态变更，以保持在美国的合法身份。
  7. H-4配偶的就业授权： 在特定情况下，H-4配偶可能有资格获得就业授权。2015年，美国政府发布了一项规定，允许H-4签证持有人中的某些配偶，只要主申请人的雇佣类移民申请（Form I-140）获得批准，或者主申请人获得超过六年的延期，就可以申请工作授权。

总之，H-4签证类别允许H签证持有人的配偶和未婚子女陪同其来到美国，并在授权逗留期间在美国居住。H-4签证持有人可以学习，但通常不被允许工作，尽管在特定情况下，某些H-4配偶可能有资格获得工作授权。

H-4 is a non-immigrant dependent visa category in the United States that is specifically designed for the spouses and unmarried children under the age of 21 of H visa holders. H-4 visa holders are allowed to accompany the primary H visa holder to the U.S. and reside in the country during the H visa holder’s authorized period of stay. Here is a detailed explanation of the H-4 visa:

  1. Eligibility: H-4 visa eligibility is contingent upon the primary H visa holder’s status. To qualify for an H-4 visa, the applicant must be the spouse or unmarried child under 21 years old of an H-1B, H-2A, H-2B, H-3, or H-1B1 visa holder.
  2. Dependent Status: H-4 visa holders are considered “dependents” of the primary H visa holder. As dependents, they are not allowed to work in the U.S. unless they independently qualify for a work visa or employment authorization through other means.
  3. Duration of Stay: The duration of an H-4 visa depends on the validity period of the primary H visa holder’s visa. H-4 visa holders can stay in the U.S. as long as the primary H visa holder maintains their status and remains in the country.
  4. Study: H-4 visa holders are allowed to study in the United States. They can enroll in schools, colleges, universities, or other educational institutions without the need to obtain a separate student visa.
  5. Travel: H-4 visa holders can travel in and out of the U.S. while their visa is valid. However, they need to ensure that their visa is still valid for re-entry if they plan to travel outside the country.
  6. Change of Status: If the primary H visa holder changes their visa status or adjusts to a different immigration status, the H-4 dependents may also need to apply for a change of status to maintain their lawful presence in the U.S.
  7. Employment Authorization for H-4 Spouses: Under certain circumstances, H-4 spouses may be eligible for employment authorization. In 2015, the U.S. government introduced a rule that allows certain H-4 spouses of H-1B visa holders with approved employment-based immigrant petitions (Form I-140) or who have been granted an extension beyond the six-year limit to apply for work authorization.

In conclusion, the H-4 visa category enables the spouses and unmarried children of H visa holders to accompany them to the U.S. and reside in the country during their authorized stay. H-4 visa holders can study but are generally not allowed to work, although certain H-4 spouses may be eligible for employment authorization under specific circumstances.