Dismissal (referred to informally as firing or sacking) is the termination of employment by an employer against the will of the employee.
Though such a decision can be made by an employer for a variety of reasons, ranging from an economic downturn to performance-related problems on the part of the employee, being fired has a strong stigma in many cultures. To be fired, as opposed to quitting voluntarily (or being laid off), is often perceived as being the employee’s fault,[1] and is therefore considered to be disgraceful and a sign of failure.
Finding new employment may often be difficult after being fired, particularly if there is a history of being fired from previous jobs, if the reason for firing is for some serious infraction, or the employee did not hold the job very long. Job seekers will often not mention jobs that they were fired from on their resumes; accordingly, unexplained gaps in employment are often regarded as a red flag.

Source: http://en.wikipedia.org/wiki/Dismissal_%28employment%29