Citizens of many countries do not require visas in many other countries. A good example of this are US citizens not requiring visas in the EU and vice versa.
Specifically for Indian Citizens, we do not require visas in many countries as well. A good example of this might be countries such as Nepal, Bhutan, Mauritius etc.
Typically this is due to diplomatic relations between the countries which may or may not be influenced by a significant population of Indian diaspora living in the foreign country. Many a times this is also due to fact that the countries are quite close to each other and would like to maintain their diplomatic relations from the past or in terms of trade.
So, in short, yes you don't require a visa for Jamaica and this is quite common all across the world for many citizens of different countries to visit other countries.