Everything you send and receive on the internet travels via your router – it is essentially the “gateway” between your PC and the internet. It decides, in part, what has access to your computer, and what doesn’t.
You find houses by their addresses, and you find computers by their IP addresses. It is basically the same principle. In order for us to expose your “offline” site to the internet, we need to point whoever requests to see it in the right direction.
There are two different “flavors” of IP address – local and global. Global IP addresses are unique and accessible to all. Local IP addresses are assigned to computers within a local network (for instance, your router will have assigned a local IP address to your computer). In order for your “offline” site to go online, we need to reveal your local IP address so that it can be found.
Internet browsers typically try to access web servers via port 80. So when Users try to connect to a Raspberry PI over Internet, the attempt will typically be made via that port. As such, we need to tell the router to redirect requests via that port to your RaspberryPI´s local IP address.
This is where the process can get complicated, because there are literally hundreds of router brands with different user interfaces. Luckily for us, there is an enormously comprehensive guide to port forwarding here.