2001:4878:4038::/48 - AKAMAI-ARIN-V6-1
AS12222 Akamai Technologies, Inc.
V6NetHandle: NET6-2001-4878-1 OrgID: AKAMAI Parent: NET6-2001-4800-0 NetName: AKAMAI-ARIN-V6-1 NetRange: 2001:4878:: - 2001:4878:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF NetType: allocation RegDate: 2005-03-17 Updated: 2015-06-25 Source: ARIN
IP address ranges, or netblocks, are groups of related IP addresses. They are usually represented as a base IP address, followed by a slash, and then a netmask which represents how many IP addresses are contained within the netblock. This format is known as CIDR. You'll also sometimes see netblocks given as a start ip address, and an end ip address, or an ip address range.
Traffic works its way around the internet based on the routing table, which contains a list of networks and their associated netblocks.