What is the difference between a local and global ip address?
Global IP is public but if you want to use a local IP address, you need a VPN Service or it is used inside a private network. If you need more info, you should visit this homepage.
Public IP address, external IP address and global IP address mean the same. This is normally your ISP/VPN/Proxy address seen by the outside World
Private IP address, internal IP address and local IP address mean the same. This is assigned by ISP/VPN/Router etc to your device and is not easily accessible to the outside World.
First we need to understand why we have two addresses, i.e. Public and Private. In IPv4, each address is represented using 4 bytes(32 bits). So the number of unique IP addresses we can generate is 2^32 or 4,294,967,296 which is about 4.3 billion. Though this may seem like a very big number, the number of devices connected to the internet is much larger ( about 8.7 billion in 2012 itself). So how do we assign an unique IP address to each device connected to the internet?
One of the solution to this question was the introduction of IPv6 which uses 128 bits for addressing. So we can have 2^128 or 3.4*10^38 unique IP addresses to uniquely identify a device on the internet. But since routers were initially designed to work with IPv4, replacing or upgrading them takes time.
So, we have two types of addresses to overcome the problem. A private address is assigned to devices within your network. This IP address is used to uniquely identify your device within the network. So, most addresses we see, have the IP address starting with 192.168.x.x. These are the private IP addresses. The devices outside your network cannot see your private address.
To communicate with the rest of the world, all the devices in your network have a single public address (which is configured in your router). So anyone outside your network communicates with you using your public address. But, all the devices in the network have a common public address. So, how will the message reach the correct device? This is done by your router which maps your public address with that of your private address. This process is known as NAT( Network Address Translation)
