Sentiment Analysis or Opinion Mining is the computational study of the attitudes, opinions and emotions of people toward an entity. The 21st century has seen the advent of the online shopping system, which has become a very popular mechanism for users to purchase goods without actually going to stores. These reviews can be referred to by other users to help them decide which products to buy. Applying sentiment analysis to these product reviews can help in understanding the overall reception of the product. Sentiment analysis has increased the interest of many researchers in recent years, since subjective texts are useful for many applications. Sentiment analysis in particular has become a great research field. Studies on sentiment analysis mainly focus on pre-processing, feature extraction and classification model construction. This paper presents a survey on various research and latest development done in sentiment analysis, and also makes an introduction of its application in various fields. And finally discuss some future scope and directions where sentiment analysis could grow.