Last year, President Obama announced an initiative to offer clemency to the non-violent drug offenders convicted under the old laws. With today's batch, Obama has now commuted the sentences for 89 prisoners, the vast majority of whom applied under that initiative.
Commutation of sentence is a form of executive clemency which reduces or terminates a sentence that an individual is currently serving. This differs from a pardon, which is granted after the sentence is completed and serves as forgiveness from the state or country.