Full employment of human and non-human resources or at least minimization of unemployment is an accepted goal of macroeconomic policy. Also the best way to alleviate poverty is to provide gainful employment to the poor.
The rate of unemployment is simply the fraction or percentage of workforce that has no gainful employment. Unfortunately there are several definitional and measurement problems. Who constitutes the labor force? One answer could be: all those who want to work. But some are not permitted by law to be employed. Some who are eligible would like to work but are not actively searching for employment. Some will accept employment only under certain conditions. All these difficulties render the definition of labor force itself problematic. Then again when is a person 'unemployed'? Some are partially employed, some get sporadic employment on daily basis, some have offers of employment but are waiting for a better offer, some are in transition from one job to another.
Despite these difficulties statisticians and economists have devised fairly good measures for labor force and unemployment. To implement these measures and estimate unemployment is a tough task. We will examine it briefly later.
One must also keep in mind that unemployment has regional, temporal and occupational dimensions. A substantial overall rate of unemployment is quite compatible with shortages of labor with specific skills or in a particular region or at a particular time of the year.