The IPv6 address itself can be quite overwhelming to look at as it is typically represented in hex, and this to many people just looks confusing, as opposed to the simply looking at the IPv4 decimal address. As shown in Figure 2, the IPv6 address is typically notated in eight 16-bit sections (keep in mind this is in hex).
To make it even more complicated, a number of different rules can be used to shorten this address based on what the actual address is. For example, if each of the 16-bit sections are all zeros, then it can be represented by just one zero, as shown in Figure 3.
Another rule allows any of these groups containing zeros and a trailing digit to drop the leading zeros, as shown in Figure 4.
Another rule allows the use of the :: as a replacement for a string of zeros; however, this can only be used once within any given notation. If you ever see an IPv6 address with two :: in it, the address is invalid or was written incorrectly. An example of this is shown in Figure 5.
As you can see, there are a number of different ways to display this type of address, and the understanding of these rules allows you to understand how the full address would be written.