The reason the Steem dollars were created is that the founders wanted to tie Steem's value to the US dollar so that people could trade inside Steemit without fear of exchange rate fluctuations. That way, if you trade, say, 100 USD Steem, you give Steem 100 USD.
The Steem dollar is just a debt acknowledgment, a promise - if and when you decide to cash your Steem dollars, you will however have a lot of Steem it takes to get that value in USD. There is also an interest earned on all remaining Steem Dollars in your account (currently 10% per annum). This is done in order to get people to leave their Steem Dollars in their account.
SBD price in November 2017
SBD began trading from INR 108.38 on 22 November 2017 and saw a dip towards INR 86.57 on 30 November 2017.
SBD price in December 2017
SBD started at INR 98.71 on 1 December 2017 and was valued at INR 516.25 on 31 December 2017.
SBD price in January 2018
SBD started at INR 574.87 on 1 January 2018 and dipped down to INR 307.03 on 31 January 2018.
SBD price in February 2018
SBD started at INR 327.22 on 1 February 2018 and took a downward leap to INR 241.11 on 28 February 2018.
About Steem Dollars (SBD):
Steemit was in beta until 4 July 2016. Once the platform (Steemit) put in contributors, the currency saw an increase of 1800% of its price from $ 0.24 to $ 4.63.
Steem is the basic cryptocurrency used to power the entire system. You can buy and sell Steem, speculate on its price or convert it into Steem Dollars and Steem Power. But if you do not want to speculate on the price or if you do not collect your Steemit profits, you do not need to deal directly with Steemit.
Steem Dollars - This is the motto of the Steemit platform and is also known as SMD. This is what people send to each other when they send messages on Steemit. The reason it's called Steem Dollar is because the Steem Dollar represents any amount of Steem required to reach 1 USD depending on the exchange rate at that time (more or less).