You should read the info over at the codex:

http://codex.wordpress.org/Child_Themes

In short – Child Themes will NOT work without a parent theme. This PARENT can either be a framework like Genesis OR it can be another parent-ready theme such as TwentyTen.

Child Themes developed for Genesis will NOT work with other parent frameworks and they will NOT work alone, you will always need the framework ALSO installed.

Basically you will always need 2 themes in your theme folder. One will be a parent theme, which could be a framework, one will be the child or LIVE theme.

You could even go as far to have child themes of child themes in a sort of Inception-style deep propagation but I wouldn’t recommend it

if u want to use the child one — u need to install genesis along , where as if u want to install classic u dont need genesis — i think i am right?

but the thing in very simple i want to ask is — why do we need genesis and child combination .
please help on this and if any simple tutorial to help on this as i heard the concept of hooks etc is being implemented. kindly help

Essentially the Genesis framework is a “middle” layer between WordPress and the Child theme.

Rather than modding the core files of a StudioPress theme and changing the code and layout to fit your needs you can instead use Genesis and create a “child” which will have its own set of rules for design and layout but lean on the principles availiable in the framework.

In theory its great for developers, in practice its no different for users or clients as they simply reap the benefits.

Let me know if you’d like to know more: contact [at] mkjones.co.uk