Hello Rahul,
Digital Marketing is a very potential and growing sector in India right now. All the companies are going online and also the customer base for online shopping or reviews are increasing day by day.
You yourself will admit that even before buying a simple item we google it once, we like to read its reviews and ratings before making the final purchase, even if the purchase is made offline. 
Today, more and more companies or even small retailers wish to come online so that their name pops up at the topmost link when you search about the product they are selling. 
So, with such a shift in customer buying habits and in the era of digitalization such courses are very very beneficial. The only thing that you need to keep in mind is that -
1) From where you doing the course, is it a reputable institution?
2) Do they provide a certificate?
3) Who will teach you, what is his or her experience?
4) The entire syllabus and the topics they will cover in what number of days.
5) And lastly, if they assist for placements because these days some of them help you to seek a job. 

Hope this helps,
Good luck!

PS: feel free to reach for any more queries.