Is opt a special name in Bash Script?

Question

I was reading an answer on Unix Stack Exchange for creating a Menu in bash. Link to which is as follows:

Arrow key/Enter menu

I'm not able to understand how opt is having content of the array. See the code if you don't want to open the link.

#!/usr/bin/env bash
Renders a text based list of options that can be selected by the
user using up, down and enter keys and returns the chosen option.

Arguments   : list of options, maximum of 256
"opt1" "opt2" ...
Return value: selected index (0 for opt1, 1 for opt2 ...)
function select_option {
# little helpers for terminal print control and key input
ESC=$( printf "\033")
cursor_blink_on()  { printf "$ESC[?25h"; }
cursor_blink_off() { printf "$ESC[?25l"; }
cursor_to()        { printf "$ESC[$1;${2:-1}H"; }
print_option()     { printf "   $1 "; }
print_selected()   { printf "  $ESC[7m $1 $ESC[27m"; }
get_cursor_row()   { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
key_input()        { read -s -n3 key 2>/dev/null >&2
                     if [[ $key = $ESC[A ]]; then echo up;    fi
                     if [[ $key = $ESC[B ]]; then echo down;  fi
                     if [[ $key = ""     ]]; then echo enter; fi; }

# initially print empty new lines (scroll down if at bottom of screen)
for opt; do printf "\n"; done

# determine current screen position for overwriting the options
local lastrow=`get_cursor_row`
local startrow=$(($lastrow - $#))

# ensure cursor and input echoing back on upon a ctrl+c during read -s
trap "cursor_blink_on; stty echo; printf '\n'; exit" 2
cursor_blink_off

local selected=0
while true; do
    # print options by overwriting the last lines
    local idx=0
    for opt; do
        cursor_to $(($startrow + $idx))
        if [ $idx -eq $selected ]; then
            print_selected "$opt"
        else
            print_option "$opt"
        fi
        ((idx++))
    done

    # user key control
    case `key_input` in
        enter) break;;
        up)    ((selected--));
               if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
        down)  ((selected++));
               if [ $selected -ge $# ]; then selected=0; fi;;
    esac
done

# cursor position back to normal
cursor_to $lastrow
printf "\n"
cursor_blink_on

return $selected

}