Affirmative action is the concept of providing a quota system to a process to favor a group which has been deemed historically discriminated. The practice is widespread throughout the world and known as employment equity, reservation or positive action.
One of the benefits of the system is it forces integration of processes such as employment or education. This allows discriminated groups the opportunity to gain access to previously denied areas of acceptance. The inclusion is assured through a quota system usually (although a percentage system is sometimes used). For example, a medical school may reserve 10 of the 100 seats only for minority groups. This ensure that at the minimum, 10 students will be minority but it does not stop minority students from having more than 10 seats.
The forced integration helps on two different fronts. First, companies and schools with diverse populations tend to be more efficient and creative over an extended period. This produces a better product. Secondly, the integration forces people to accept, if on a superficial level, minority groups which can lead to better social interactions.
Integration can also help with pay, benefits, recognition and opportunity which are often points of tension among different groups. Equality through affirmative action can decrease this tension and allow for better social quality of life.
There are negatives to affirmative action as well. One drawback is the standards for affirmative action and traditional applicants may be different. For example, if traditional students are required to score a 90% to enter law school, but not enough minority students can reach the mark it may be lower for minority groups to ensure the quotas are met. This can result in jealousy among traditional students and a lower graduation rate for minority groups which may be perceived as discriminatory.
Another argument against affirmative action is the hypocritical nature of the program. If there are special amendments for minority groups, then is everyone really equal or are minority groups more equal for certain jobs? Once again, companies may wish to promote a less qualified minority to meet affirmative action which is a form a discrimination against another person due to their personal characteristics.
The last argument I'll mention is the lower standard begets lower application. This means if minority groups are held to lower standards, then the minority group is less likely to achieve higher goals simply because they do not see the need.