What is credit rating and how does it affect a country's economic outlook?

Rahul Gandhi in his press conference on Tuesday claimed that Narendra Modi government does not want to give money to the poor as it will cause a dip in the credit rating of Indian economy. The former Congress President asserted that the Modi government should not pay attention to the credit rating and provide Rs 7,500 directly to the poor. But is it that simple? What is credit rating and how does it affect a country's economic outlook?