2001:67c:1388::/48 - RTLTD2
inet6num: 2001,67c,1388,,/48 netname: RTLTD2 country: GB org: ORG-RT6-RIPE admin-c: DP3028-RIPE tech-c: DP3028-RIPE status: ASSIGNED PI mnt-by: RIPE-NCC-END-MNT mnt-by: RTLTD-MNT mnt-by: MNT-INIT7-NOC mnt-routes: RTLTD-MNT mnt-routes: MNT-INIT7-NOC mnt-domains: RTLTD-MNT mnt-domains: MNT-INIT7-NOC created: 2013-02-25T12,51,01Z last-modified: 2016-04-14T09,51,57Z source: RIPE sponsoring-org: ORG-KFL2-RIPE organisation: ORG-RT6-RIPE org-name: Ready Technology (UK) Limited org-type: OTHER address: 2nd Floor, 145-157 St John St address: London address: EC1V 4PY address: GB e-mail: email@example.com abuse-c: AR18746-RIPE mnt-ref: RTLTD-MNT mnt-by: RTLTD-MNT created: 2005-10-02T23,21,04Z last-modified: 2014-03-03T11,32,03Z source: RIPE person: Daniel Pocock address: 2nd Floor address: 145-157 St John Street address: LONDON EC1V 4PY address: United Kingdom phone: +44 207 1357000 nic-hdl: DP3028-RIPE mnt-by: RTLTD-MNT created: 2005-10-02T23,05,17Z last-modified: 2013-02-28T19,32,54Z source: RIPE route6: 2001,67c,1388,,/48 descr: Ready Technology (UK) Limited origin: AS34446 mnt-by: RTLTD-MNT mnt-by: MNT-INIT7-NOC created: 2013-02-28T19,36,01Z last-modified: 2013-02-28T19,36,01Z source: RIPE
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.