2a01:90:400::/48 - VXTR-IPV6-ANYCAST-1
inet6num: 2a01:90:400::/40 netname: VXTR-IPV6-ANYCAST-1 descr: vXtream Ltd country: US admin-c: VN2751-RIPE tech-c: VN2751-RIPE status: AGGREGATED-BY-LIR assignment-size: 48 mnt-by: uk-vxtream-1-mnt notify: firstname.lastname@example.org created: 2011-08-02T10:59:24Z last-modified: 2018-03-26T10:01:20Z source: RIPE role: vXtream NOC address: vXtream Ltd address: 260-266 Goswell Road address: London address: EC1V 7EB e-mail: email@example.com admin-c: VS10009-RIPE tech-c: VS10009-RIPE nic-hdl: VN2751-RIPE mnt-by: uk-vxtream-1-mnt created: 2017-05-18T06:40:35Z last-modified: 2017-05-18T10:12:23Z source: RIPE route6: 2a01:90:400::/40 descr: vXtream Ltd descr: Qube Managed Hosting Inc. descr: Anycast IPv6 Allocation origin: AS29668 mnt-by: uk-vxtream-1-mnt created: 2011-03-18T11:46:29Z last-modified: 2018-03-28T07:55:10Z 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.