inet6num: 2404::/26 netname: ETWEBS-TWNIC-TW-20060125 descr: Asia Pacific Online Service Inc. descr: 3F., Building C,No.19-6,Sanchong Road,Nan Kang Dist. descr: Taipei 115,Taiwan country: TW admin-c: HE6-AP tech-c: HE6-AP mnt-by: MAINT-TW-TWNIC mnt-lower: MAINT-TW-TWNIC status: ALLOCATED PORTABLE last-modified: 2008-09-04T06:49:19Z source: APNIC
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.