What is "culture" and how the term is realted to social inequality,
and why the term might be seens as "revolutionary". What problems can
be seen in the use of this concept of anthropoligal work?

Here are some ideas that may help you...  my humble opinions..

"Culture" - a collection of societal mores that have evolved within a
discrete group of people over time.  Including traditions, religious
beliefs, laws and customs, etc.

The term might be seen as revolutionary in that the term, by
definition, asserts that history (the passage of time and events)
holds power over our belief systems.  Branches of modern Liberalism
theorize that history is a normative force that guides the progress of
mankind.  Specifically, that with each revolution we progress to
increasingly egalitarian societies (despotism -> monarchy -> republic
-> democracy -> ?).  So, if we allow ourselves to believe that
revolution equates with progress, one can justify the act of
revolution as being not just beneficial to society but also the
inexorable path we must eventually walk down. This is, of course, a
dangerous idea.  Just think of the atrocities that have been commited
in the name of "social good" and revolution and you can see why.

Also, by identifying people as belonging to a specific culture we give
that culture a label, e.g. Arabs or Blacks. Labelling allows for
discrimination.  Discrimination then allows for ostracism.  Ostracism
can lead to violence or civil war or whatever else you can dream up. 
It all begins with labelling and characterizing groups of people,
which is made possible by "culture".