Hi Madhu,

make config:
Is a text-based configuration. The options are prompted one after another. All options need to be answered,
and out-of-order access to former options is not possible. Try this *once* so you have the experience but after that stay away just too much work and grief.

make menuconfig:
An ncurses-based pseudo-graphical menu (only text input). Navigate through the menu to modify the
desired options. Within menuconfig, use the / key to search modules by name.

make defconfig:
Generates a new config with default from the ARCH supplied defconfig file. Use this option to get back the
default configuration file that came with the sources.

There are lot's of other options read the section under configuration targets: https://www.kernel.org/doc/makehelp.txt

Hope this helps.

Aruna