What does it mean in parentheses?

[ttsite]

192.168.57.{103,2,102}
What does 103.2.102 in brackets mean?Is this 2.102 different for every machine? Thank you!
root@kali:/Seth-master# ./seth.sh eth1 192.168.132.{133,2,102} calc
███████╗███████╗████████╗██╗ ██╗
██╔════╝██╔════╝╚══██╔══╝██║ ██║ by Adrian Vollmer
███████╗█████╗ ██║ ███████║ [e-mail]
╚════██║██╔══╝ ██║ ██╔══██║ SySS GmbH, 2017
███████║███████╗ ██║ ██║ ██║ https://www.syss.de
╚══════╝╚══════╝ ╚═╝ ╚═╝ ╚═╝
[] Spoofing arp replies...
[] Turning on IP forwarding...
[] Set iptables rules for SYN packets...
[] Waiting for a SYN packet to the original destination...
[!] Something went wrong while parsing the output of tcpdump
[] Cleaning up...
[] Done.
root@kali:/Seth-master#

[Adrian Vollmer]

It's called shell expansion: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_04.html

Everything else you need to know is documented.

I'm sorry, but this is only meant for bugs and feature requests, not general support