Part-time MBA programs are designed for working professionals.
Most part-time MBAs work full-time during the day and attend classes in the evening.
Some schools offer both a full-time and a part-time program.

Here are some considerations when exploring part-time programs.

Courses are scheduled year 'round and do not allow for internships.
Some part-time programs offer the same ability to specialize (through concentrations and open electives) as full-time programs, but others only offer a limited number of concentrations.
Some part-time programs require fewer courses than their full-time counterparts. Their curriculum usually includes a core body of knowledge and does not offer the ability to specialize.
Some part-time programs require the same number of courses as a full-time program, but spread out over a longer time. For example, you might take one to two courses at a time over four or five years for a degree requiring 20 courses.
Part-Time Advantages
Part-time programs are popular among career enhancers (who have a good foundation of experience and want to further their career in a chosen field). They are also good if you already have a network in your field to aid in a job change.

The following are also advantages:

Work-related
Classes are scheduled outside standard business hours.
Students develop new skills without interrupting current employment.
Students can bring current, real-world problems into the classroom and explore workable solutions they can implement on the job.
Financial
Loan money is available for eligible students.
Part-time may be a good choice if your employer offers tuition reimbursement as an employee benefit.
The cost is spread over a longer period of time, helpful to those who must continue to earn an income or who are unwilling or unable to take on more debt.
If you can't relocate
Part-time programs may offer some geographic flexibility if you are unable or unwilling to relocate. A two-hour commute might be palatable for one class a week, but not daily.

Part-Time Limitations
You should consider the following things when deciding whether a part-time program is right for you.

Scholarship money may not be available, because you can work and spread out the expenses over time.
Career services may be limited. Many placement offices are closed in the evenings, when part-time students are on campus. This practice varies widely but is of particular concern for people who wish to change careers once they receive their degree.
If you travel or relocate frequently for work, you may have difficulty completing a part-time MBA degree. Some programs do allow students to fulfill some course work through distance learning, but you should check the flexibility of the programs you are considering.
Do not assume that you can take some MBA courses part-time, then transfer to a full-time or other kind of program. Most programs do not accept transfer credits.