what is a bar
What is the context? "Bar" can have many diverse meanings. A solid rod; a brick-like shape (bar of soap or gold); a unit of pressure; a tavern; a sandbar; the practice of law.
Consult a dictionary for the meaning that makes sense. http://www.thefreedictionary.com/BAR
It can also be a verb
Could you be referring to a bar diagram?
http://images.google.com/images?client=safari&rls=en&q=bar+diagrams&oe=UTF-8&um=1&ie=UTF-8&ei=brsjS6m_B4bGsQPK77TgDg&sa=X&oi=image_result_group&ct=title&resnum=1&ved=0CBQQsAQwAA
I hope this helps.