Arpspoofing lab : eJPT

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 ( ? 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 -r ’
where is client and is server

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

will : ‘arpspoof -i interface -t -r’ 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 ??