@ saharish and amk

Yaar saaf saaf bata do naaa.

Anyway, i try to explain for the young ppl. here as they are entering in practical life.

"Chai Pani" is a deep rooted cultural practice in the sub-continent and it is eqvialent to 'TIP' in english culture. When u r happy with the services provided by a petty official like constable, postman, hospital attentand, peon etc. u pay him a small amount as a return for his promot service. The amount can vary in different circmstance and it is not mandatory. It should not be confused with "rishwat" as rishwat is usually paid to get an illegal work done.
Hope u ppl. understand now.