Business casual is a style of dress that falls in-between casual and formal clothing. It originated in the workplace, but is appropriate for a much broader array of settings. For men, it is more formal than wearing a polo and jeans, but is more casual than wearing a suit and tie. It is appropriate for a wide number of workplace settings and is becoming more common in the business workplace as time progresses.
See the following for a list of the required components of any business casual outfit and a list of settings where business casual dress is appropriate and recommended. Also, be sure to read more about regional, industry, and company differences in business casual dress codes. Each of these groupings will have a slightly different definition of business casual, so you should be to review them for your specific situation.