What are these IP addresses, how does it work, and why?

Question

Computer networks

On the interface through which it is connected to the provider (PPPoE), these are the addresses:
Inet addr: 172.18. *. *
PtP: 10.80.127.126
Mask: 255.255.255.255

The first is a white ip
The third is the mask (why is the mask 32?)
The second is Don't know

Answer 1

The first is a gray IP, the second is the same, the third is a mask of 32.
Your provider requires authorization through ppp.
The first address receives an interface from the operator's DHCP server to access the ppp server.
The second address is given to the ppp interface after authorization on the ppp server.
And you access the Internet through the NAT operator with its white address, which is not on your list.

Answer 2

PPPoE (Point-to-point protocol over Ethernet)
mask is not particularly important. address 10.80 - address of the PPPoE server through which 172.18 is broadcast to you
.

Answer 3

Inet addr:172.18.*.* is the IP address of the internal network ("gray" IP)
PtP:10.80.127.126 is the internal network address of the PTP connection
Mask:255.255.255.255 is the mask indicating that the address 10.80.127.126 is this is a self-network (8x4=32)