[Advaita-l] Svadharma and Paradharma

[Girish Ramadurgam]

NOTE; I am a novice and want to learn and hence my questions might sound 
trivial to many learned people.
I do not intend to agitate any of you, but hope that this forum can help 
me. I need to get my basics right..

In Bhagavad Gita Lord talks about Svadharma and Paradharma. Can anyone 
explain what they really mean.
What does Svadharma/Paradharma depend on?
What defines an individual Svadharma/Paradharma?

What I am trying to establish is - What can the difference in two people 
of the same age be to defined Dharma. Should someone's social status, 
situation etc. defined Dharma.

Thank you very much for your time.

Girish