I took 4 classes in networking. I have a doubt. If I am downloading something from say mp3skull.com . My private ip address is say 10.155.23.143 and ip address of company A, which provided me the private ip, is 10.155.23.22 and lets say some other company bought an Ip address 10.155.23.143. the songs server will send the packets to my ip address which is 10.155.23.143 but it will reach company B. how am I still able to receive packets?
Your private IP address, 10.155.23.143, can't be sold to anyone. All of the private ranges are reserved for internal use and will not be sold as public addresses.
What happens is that your router will translate your private IP address into an individual (or shared) public IP address owned by your ISP. Then any packets which are part of your communication stream will be directed back to your individual machine. Your private IP address never leaves your network. This is referred to as Network Address Translation, or NATing, and helps delay the problem of running out of IPv4 addresses.