A system for determining which and when people can immigrate to the U. S. within the limits of immigration set by Congress. In family immigration preference is based on the status of the petitioner (American citizen or lawful permanent resident) and his/her relationship to the applicant. Visit our Family Based Immigration webpage for more info. In employment immigration it is based on the qualifications of the applicant and labour needs in the U. S. Visit our Employment Based Immigration webpage for more info.