In USA, you will see that people have a zeal to learn new things no matter what their age is. Adult education and continuing education are some common terms used in USA for the courses done for degree credit or just for personal enrichment, self-learning, skill development and professional growth. It generally involves courses done after undergraduate studies.
Many universities have a continuing education division offering such courses. This division is more famous as Extension School. Courses are offered through normal classroom teaching, or as distance course via online access and web conference. People pursue them often as part time, for example, many professionals who work full time enroll for evening courses.
One of the benefit of enrolling into these courses is that you may find your fellow classmates from various countries, diverse cultures, different profession and variant age groups. Few courses, which are offered online, often attract students around the world. At times, you even get the opportunity to work in groups assignments which would facilitates the learning process.
Different universities offer courses on vast variety of topics and cover various fields. All universities have different requirements for enrollment. For some, only TOEFL score is enough for enrollment in certification course. Websites of some of the famous extension schools of the top universities of USA are given below.