Hi Nitin...
Many URL can be suggested with particular keyword .for example: i somebody sells herbal ayurvedic products those have medicinal effects also...now you have keyword herbal, ayurvedic, products...with the help of these keywords you may make as many URL you want.
www.abc.com/herbal products
www.abc.com/herbal medicine
www.abc.com/herbal ayurveda medicine
www.abc.com/herbal supplements
whatever keyword suits your business...
for second question....Fro SEO side it is necessary to have same keyword(which tells about your business in first visiting)..because it helps to find your business fast.
Jan 24, 2013