Section, sub section and article.

See,Articles are Bye-Laws ( I am assuming you're referring the Articles of Association of Companies), In case of constitution of India, Which is a bye law of India( Provides Rights, duties, Powers etc.)also divided into Articles,

Sections are of any law/Act which inherit it's powers from constitution ,Like companies act
Section -(Heading or title)

For the sake of convenience such sections are again divided into different sub-sections ,and if sub-section is further divided then it called(Clause)& further division called(sub-clause)..

There is also a difference between Rules and Regulations, While Rules are being sub-ordinate to law/act{through parliamentary process},while regulations are created by statutory body {IE. SEBI} within it's scope of jurisdiction...