What are reserved constituencies?

What are reserved constituencies?
Why do you think that these constituencies have been created?

A country is divided into many separate units or areas for the purpose of holding elections. Each area in which elections are held is known as a constituency. People living in a constituency elect their own representative from their constituency. A reserved constituency is one which is reserved for scheduled tribes and castes in both Parliamentary and Assembly Elections. General candidates are not allowed to contest elections from these constituencies.

Reserved constituencies were created because it was felt that in an open electorate system people belonging to certain weaker sections of society may not get a fair chance to contest and win elections. Rich, influential and powerful people may prevent the people of certain weaker caste or tribe from contesting elections which will go against the democratic spirit of the Constitution.