I am planning to launch a new web application and I expect a good number of visits, so is load balancing beneficial? In what scenarios it is beneficial?
Load balancing is typically useful for two reasons:
First, if you have more load than a single server can handle, you'll need one or more load balancers to distribute incoming load between two or more back-end nodes.
Second, if you want to be able to do maintenance on a server without it adversely affecting your visitors. In this case, you could remove one server from your load balancing rotation, perform the needed maintenance, and then put it back into rotation. Wash, rinse, repeat.
You need load balancing when you want either higher capacity than a single machine can provide, or higher availability than a single machine can provide, or both. Whether you need it in your scenario is impossible to say based on the information you've given, and in my experience it is almost impossible to provide enough information in a Server Fault question to allow such a question to be answered, yet keep the question general enough to avoid it being closed as "Too Localised".
My recommendation would be to either wing it and see (very, very dangerous), or enlist the services of someone who knows what they're doing to ensure that your scaling is taken care of.