The 'u' in front of the string values means the string is a Unicode string. Unicode is a way to represent more characters than normal ASCII can manage. The fact that you're seeing the u means you're on Python 2 - strings are Unicode by default on Python 3, but on Python 2, the u in front distinguishes Unicode strings. The rest of this answer will focus on Python 2.
You can create a Unicode string multiple ways:
>>> u'foo'
u'foo'
>>> unicode('foo') # Python 2 only
u'foo'
But the real reason is to represent something like this (translation here):
>>> val = u'Ознакомьтесь с документацией'
>>> val
u'\u041e\u0437\u043d\u0430\u043a\u043e\u043c\u044c\u0442\u0435\u0441\u044c \u0441 \u0434\u043e\u043a\u0443\u043c\u0435\u043d\u0442\u0430\u0446\u0438\u0435\u0439'
>>> print val
Ознакомьтесь с документацией
For the most part, Unicode and non-Unicode strings are interoperable on Python 2.
There are other symbols you will see, such as the "raw" symbol r for telling a string not to interpret backslashes. This is extremely useful for writing regular expressions.
>>> 'foo\"'
'foo"'
>>> r'foo\"'
'foo\\"'
Unicode and non-Unicode strings can be equal on Python 2:
>>> bird1 = unicode('unladen swallow')
>>> bird2 = 'unladen swallow'
>>> bird1 == bird2
True
but not on Python 3:
>>> x = u'asdf' # Python 3
>>> y = b'asdf' # b indicates bytestring
>>> x == y
False
