I just recently learned about IPv4 and the different classes. Let's say I have a following arbritary IP address : 220.127.116.11
From that, I deduce that the first octet (12) in my class is the network ID and the remaining 123.123.45 is the host ID. Now my question is, first of all,
Q1: is network ID (12) the same for everyone on my ISP?
Q2: Why do all devices on my home network share the same IPv4 address? Surely, the hostID part for each of them should change?
In essence, I'm asking what do these NetIDs and HostIDs actually repersent, is a part of the HostID meant to repersent my router? Which part does everyone on my ISP share?