Difference between unicodecsv and csv

In python what is actual difference between unicodecsv package and csv package? while printing elements in csv file when imported by unicodecsv it is printed along with character u

import unicodecsv
ion = []
f = open('csvlear.csv','r')
pop = unicodecsv.DictReader(f)
for i in pop:
    ion.append(i)
    print(i)
f.close()

output:

{u'age': u'1'}
{u'age': u'2'}
{u'age': u'3'}
{u'age': u'4'}

instead of importing unicode if csv package is imported, the character u is omitted.what is the difference