"Please explain me the difference between private IP address and non private one"
When the Internet was first designed, no one thought there'd be a need for more than a few billion addresses. So an addressing scheme with four numbers, each 0-255 seemed like a big enough set of addresses to be in use forever.
They didn't count on seven billion people having computers and smartphones and smart TV's and refrigerators with Web browsers and... well... 4294967296 IP addresses was getting used up, FAST. So some really smart guys are trying to get the world to move to a new address called IPv6.
In the meantime, though, some other smart guys thought up this thing called address translation. Their idea was to "reserve" some IP address ranges for use in private networks. 10.x.x.x, 192.168.x.x and some others. By a techie agreement called RFC1918, no Internet switch or router will deal with these "reserved" addresses.
We use these "reserved" ranges to create private networks with "private" IP addresses. I'm at work right now using an address of 172.16... When I come to WIMI, I pass through a router that my employer operates. On the "inside," everything is 172.whatever. On the "outside," the router is running a very complicated database that "translates" my 172 "private" address to a proper Internet IP address. And then "translates" the bits and bytes back to my 172 address when WIMI responds back to me.
The details can make some peoples' heads spin. But that's the nickel tour of network address translation (NAT, for short).