What is $opt variable for command line parameter in bash

Question

I have below bash script, I am a bit confuse about what is $opt meaning. and I do not find detail information about it after search.

test.sh:

echo

Answer 1

the for statement goes generally like this:

for x in a b c; do
  ...
done

$x has the value a on the first iteration, then b, then c. the a b c part need not be written out literally, the list to iterate through can be given by a variable, like the $@, which has the list of all arguments to the current scope:

for x in "$@"; do
  ...
done

further, in "$@" is assumed if you provide no list explicitly:

for x; do
  ...
done