Arpspoofing lab : eJPT

HI
In the arp poisoning lab , i have 2 doubts –

a) i am not able to get how come telnet credentials were found in wireshark … Is there a telnet attempt made in background frm client to server (10.100.13.36) ? Like : are you running a script in background which telnets from client to server so that we can spoof the packet

b) you have taken command 'arpspoof -i interface -t 10.100.13.37 -r 10.100.13.36 ’
where 10.100.13.37 is client and 10.100.13.37 is server

as per syntax -t is target and -r is host

will : ‘arpspoof -i interface -t 10.100.13.36 -r 10.100.13.367’ give similar results

Although lab steps works , but I am not clearly able to get the message of what are we trying here ?
As a kali machine [ hacker ] , are we tryng to intimitate ourselves as 10.100.13.36 ??