AS4637 Telstra Global
2405:f100:1::/48 - ATS-SG
inet6num: 2405:f100::/32 netname: ATS-SG descr: 10 Pasir Panjang Road descr: #10-01 Mapletree Business City descr: (wef: 1May 2011) country: SG admin-c: ATSP2-AP tech-c: ATSP2-AP mnt-routes: MAINT-ATS-SG mnt-irt: IRT-ATS-SG mnt-lower: MAINT-ATS-SG mnt-by: APNIC-HM status: ALLOCATED PORTABLE last-modified: 2012-12-12T04:05:08Z 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.