give me a general concept of it

Dear Noble Researcher, 

If you search the web for [defnition:"greenhouse effect"], you'd have
many sites describing and defining it.

A definition from several dictionaries is available on Dictionary.com
<http://dictionary.reference.com/search?q=greenhouse+effect&r=67>

Explanation Guide has a very good one
Greenhouse effect - explanation-Guide.info
<http://explanation-guide.info/meaning/Greenhouse-effect.html> 

I hope this answers your question. Please contact me if you need any
clarification on this answer before you rate it.

See:  http://en.wikipedia.org/wiki/Greenhouse_effect

It has a good explanation.

From the summary there:

"The "greenhouse effect" is the process by which an atmosphere warms a
planet. Mars, Venus and other celestial bodies with atmospheres (such
as Titan) have a greenhouse effects, but for simplicity the rest of
this article will refer to the case of Earth.

The term greenhouse effect may be used to refer to two different
things in common parlance: the natrual greenhouse effect, which refers
to the greenhouse effect which occurs natrually on earth, and the
enhanced (anthropogenic) greenhouse effect, which results from human
activities (see also global warming). The former is accepted by all;
the latter is a matter of some dispute."