Law school
A law school is an educational institution that trains lawyers. It is universally required for lawyers in the United States. Typically, a student must spend three years in law school to earn a J.D. (Juris Doctor, Latin for 'doctor of law') degree. Some law schools may also offer a PhD in law. Most prospective lawyers need an undergraduate degree to be admitted, and admission to law school is competitive. A J.D. degree, along with passing the bar examination, will grant a person legal license to work as an attorney.
Universities
There are roughly 200 law schools in the United States, most of which are part of a larger university. The most prestigious law schools are themselves within prestigious universities, such as Harvard Law School. Technical (science-focused) institutes and liberal arts colleges are unlikely to have an attached law school.
Admissions
Law schools are selective in their admissions, and the occupation of a lawyer is highly desired. The Law School Admission Test (LSAT) is universally taken by applicants, assessing one's abilities in logic and reading.