LINE is an application for making free calls and sending free messages from your mobile phone via the inteet. In fact, this is another Skype, but with a greater bias towards social communication, because. in addition to the main purpose, you get your personal page and the ability to make new friends, as in the WhatsApp application.
To update the application, install the new version of the application over (without deleting) the old one.
This update will only be possible if the previous version of the application is downloaded from us. Otherwise, there will be a signature conflict and you will see the message "Application not installed".
For what "Signatures" are and what they are for, read here.