Private IP address

What is private IP address:

• A private IP address is an IP address that's reserved for internal use behind a router or other Network Address Translation (NAT) device, apart from the public.

Which IP Addresses Are Private?

• The Internet Assigned Numbers Authority (IANA) reserves the following IP address blocks for use as private IP addresses:
• 10.0.0.0 to 10.255.255.255     ==> 16 million addresses
• 172.16.0.0 to 172.31.255.255    ==> 1 million addresses
• 192.168.0.0 to 192.168.255.255   ==>  65,000
• Another range of private IP addresses is 169.254.0.0 to 169.254.255.255, but those addresses are for Automatic Private IP Addressing (APIPA) use only.
• In 2012, the IANA allocated 4 million addresses of 100.64.0.0/10 for use in carrier-grade NAT environments.

Why using Private IP address:

• IP address are limited, so private IP addresses provide an entirely separate set of addresses that still allow access on a network but without taking up a public IP address space.

Reserved IP Addresses

• Another set of IP addresses that are restricted even further are called reserved IP addresses.
• These are similar to private IP addresses in the sense that they can't be used for communicating on the greater internet, but they're even more restrictive than that.
• The most famous reserved IP is 127.0.0.1. This address is called the loopback address and is used to test the network adapter or integrated chip.  
• Technically, the entire range from 127.0.0.0 to 127.255.255.255 is reserved for loopback purposes but you'll almost never see anything but 127.0.0.1 used in the real world.
• Addresses in the range from 0.0.0.0 to 0.255.255.255 are also reserved but don't do anything at all. If you're even able to assign a device an IP address in this range, it will not function properly no matter where on the network it's installed.

Source:
     https://www.lifewire.com/what-is-a-private-ip-address-2625970