Usualy you need to show to your cliente, friend or anyone your website or show what your are doing locally, but you don't have a host yet or do not have enought time to publish it, or just want to show online one change, so this is one of the super power of NGROCK, this program are awesome for developer and I'm pretty sure for more people. What NGROK does is put online your http ports(tunneling) and make it accesible for anyone by a simple URL generated by this tool.