$* is all the parameters to the script or function, split into separate arguments on whitespace.
If you have a function:
for x in $*
foo 1 "2 3 4" 5 will output:
That is, the quoted string
"2 3 4" will be split into three separate "words".
When you don't want to split the arguments into separate words like that, you can use
$@. If the same function used
"$@" in place of
$*, it would output:
2 3 4
That is, the quoted string would not be split into separate words. This is like listing all the positional parameters out explicitly:
"$1" "$2" "$3" "$4" .... In general, this is probably the one you want to use - the word-splitting will often lead to nasty bugs that are hard to track down.
At the top level of a script (not inside a function), these refer to the arguments given to the script itself.
Your example is calling either
run_test with all of the arguments to this script or function, split into separate words. If the script were run as
script.sh "hello world" 2 3 then it would have the effect of running:
run_command hello world 2 3