127.0.0.1 is the IP address for local machine. That means the machine you are working on and it is the same for all of us (we all have this). This line should not be messed with.
127.0.1.1. Section 10.4 of the debian manual:
Some software (e.g., GNOME) expects the system hostname to be resolvable to an IP address with a canonical fully qualified domain name. This is really improper because system hostnames and domain names are two very different things; but there you have it. In order to support that software, it is necessary to ensure that the system hostname can be resolved. Most often this is done by putting a line in /etc/hosts containing some IP address and the system hostname. If your system has a permanent IP address then use that; otherwise use the address 127.0.1.1.
Is added due to this bug: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=719621
Both of these IPs are IPv4. Since the world is running out of IP addresses there is also IPv6. Where IPv4 uses 4 numbers from 0 to 255 (roughly; so 2**32 permutations) IPv6 addresses are 128 bits long (so 2*128 permutations) used in 8 groups of 4 hexadecimal digits.
::1 ip6-localhost ip6-loopback
are all IPv6 versions. ::1 is the IPv6 version of 127.0.0.1 so also means local host.
These are multicast addresses:
Well-known IPv6 multicast addresses
ff02::1 All nodes on the local network segment
ff02::2 All routers on the local network segment
ff02::5 OSPFv3 All SPF routers
ff02::6 OSPFv3 All DR routers
ff02::8 IS-IS for IPv6 routers
ff02::9 RIP routers
ff02::a EIGRP routers
ff02::d PIM routers
ff02::16 MLDv2 reports (defined in RFC 3810)
ff02::1:2 All DHCP servers and relay agents on the local network segment (defined in RFC 3315)
ff02::1:3 All LLMNR hosts on the local network segment (defined in RFC 4795)
ff05::1:3 All DHCP servers on the local network site (defined in RFC 3315)
ff0x::c Simple Service Discovery Protocol
ff0x::fb Multicast DNS
ff0x::101 Network Time Protocol
ff0x::108 Network Information Service
ff0x::114 Used for experiments