OTG stands for On-The-Go. It is a feature with which you can connect various external devices with your phone to perform different things. You can connect a mouse, keyboard, gaming console, pen drive and even another phone. With pen drive/hard disk and mobile phones, you can extract data from them, thus reducing the hassle to save everything on your smartphone. It saves memory on your smartphone and also makes it easy to transfer files.
With keyboard and more, you can easily turn your smartphone into a laptop and can work while you're on-the-go. Adding to it, you can connect your smartphone to the TV as well.