In the USA, a GED functions exactly the same way as a high school diploma.
A proficiency certificate also allows minors to be employed without a work permit or other restrictions.
A GED or similar is not sufficient to be accepted to university alone, but most tertiary education institutions require a diploma or equivalent. To get into any place of prestige you'll need a competitive GPA at a community college or high school, extracurriculars, good SAT/ACT, the works. Same as anyone else.
GED stands for:General Education Development