Would you like to hone(*) your professional skills from the comfort of your home or get a college degree without setting foot on campus? Sound too good to be true? There are now thousands of online classes available on the World Wide Web and that number will soon mushroom(*) into tens of thousands.

For decades(*), students have turned to distance learning to further their educational goals. From correspondence(*) courses to tele-classes, distance learning has served the needs of people who cannot physically attend classes. With the explosion of information technology and the Internet, you can now have a virtual classroom right on your desktop. In most cases, to take a course you need only your computer, a web browser and Internet access.

A New Kind of Education

Online learning, also known as Web-based training or WBT, makes it possible to deliver instructional content to your personal computer via the World Wide Web. You access a website, where you will find most, if not all of the materials you need--a course outline and lessons, information about the instructor (if there is one), lecture notes, a list of activities, tests, and inks to other online resources. In some cases, additional materials may be required, such as textbooks or videotapes. Some WBT class are self-paced, others are led by an instructor. Most are what is known as asynchronous(*) classes--you study at your convenience--although there may be a period of time in which you must complete the course.

WBT offers a number of advantages over classroom-based instruction:

　　Take a class anywhere. Learn at home or at the office, because you only need a computer and Internet access.
　　Take a class anytime. Access material 24 hours a day, seven days a week.
　　You decide when to attend. Take courses according to your own schedule and pace.
　　Lower costs. Eliminate(*) travel, parking, childcare and all the other costs of physically attending a class.
　　Instant feedback(*). Tests can be graded and returned to you within seconds.
　　Access to the latest materials. Instructors can easily update teaching materials as new information becomes available. Most textbooks are out-of-date(*) before they are even printed.
　　An interactive(*) learning environment. Online technologies enable interaction with other students and course instructors.

Online learning has disadvantages too, the main one being that students work in isolation. To overcome this problem, many WBT classes incorporate features that invite student participation and collaboration(*) including:
　　E-mail for submitting homework and communicating with the instructor and other students.
　　Message boards where students can post messages relating to class content and group activities.
　　Chat rooms, audio conferencing and videoconferencing for real-time conversation.
　　Screen-sharing, which allows students to see what an instructor demonstrates on his or her computer screen.
　　Class websites for posting of charts, graphics, links to other resources, etc.

Not all classes require student participation. Most use only a few of the features just discussed. Since education on demand is so new, course providers are trying to figure out what works best. And since people learn in different ways, classes vary in style. With self-paced classes, you study the course material and possibly take some online quizzes(*). Either no instructor is involved, or there may be a "teaching assistant" who can answer questions via e-mail. Because little human intervention is required, enrollment(*) is open to any number of students and you can begin the course as soon as you register.

Instructor-led classes are more demanding, often requiring that you submit homework assignments, meet online periodically with other students enrolled in the class, and participate in real-time class discussions with an instructor. These types of classes generally limit enrollment (perhaps to under 50 students) and have a start and end date. Upon completion of a class you may receive a grade. Classes offered by universities typically follow this model.

Subjects and prices vary enormously(*), ranging from accounting to zoology; some classes are free, while others cost hundreds of dollars.

Is Online Learning for You?
Typically, online classes are targeted(*) to working adults--people who want to get an advanced degree or acquire new skills for their jobs, but don't have time to regularly attend classes. Classes are open to anyone, but you may need some prerequisites(*) before you can enroll in certain courses. The requirements are usually listed along with class descriptions.
Online learning works best for people who are self-motivated, enjoy working alone at their computer and feel comfortable using technology. Beyond that, it's just one of those things you have to try.

　　注释：

　　hone：磨练 ；用磨刀石磨
　　mushroom：vi. 迅速生长, 迅速增加, 采蘑菇
　　decade:十年
　　correspondence： n. 相应, 通信, 信件
　　asynchronou：不同时，异步
　　eliminate: vt. 排除, 消除 v. 除去
　　feedback:回授, 反馈, 反应
　　out-of-date:过时
　　interactive：交互式的
　　collaboration:协作
　　quizzes：被检测者
　　enrollment：登记，注册
　　enormously：非常地，巨大地
　　targeted：n. 目标, 对象, 靶子
　　prerequisites：特权