$* is a single string, whereas $@ is an actual array

To see the difference, execute the following script like so:

 > ./test.sh one two "three four"

The script:

#!/bin/bash

echo "Using \"\$*\":"
for a in "$*"; do
    echo $a;
done

echo -e "\nUsing \$*:"
for a in $*; do
    echo $a;
done

echo -e "\nUsing \"\$@\":"
for a in "$@"; do
    echo $a;
done

echo -e "\nUsing \$@:"
for a in $@; do
    echo $a;
done              

The four cases are:

Using "$*":
one two three four

Here, the parameters are regarded as one long quoted string. Unquoted:

Using $*:
one
two
three
four

The string is broken into words by the for loop.

Using "$@":
one
two
three four

This treats each element of $@ as a quoted string.

Using $@:
one
two
three
four

This treats each element as an unquoted string, so the last one is again split by what amounts to for three four.