I found this to be a great way to not have to go through and manually add any of my friends from my phone, so it came in really helpful to me.
The other functions that I found very useful was that I could search for people nearby and start chatting with them if all of my friends were busy. It also has stickers (kind of like emojis) that you can use to make your chat more fun and animated.
You can also add an avatar to your account and play games with LINE App which makes it a really fun free app to use to keep in touch with people from around the world at anytime. I found that it was a great way to keep up to date with all of my contacts from overseas with only needing to have WiFi connection.