Variadic Templates - Parameter pack expansion understanding

I am having a hard time understanding parameter pack expansion. The thing that confuses me are when dots appear on the right side and when dots appear on the left side. I came across this post which helped a little. Suppose I have the following two examples

Example 1:
template <class ...A>   --> line 1
int func(A... arg)      --> line 2
{
   return sizeof...(arg);
}

int main(void)
{
   return func(1,2,3,4,5,6);
}

The post I mentioned above I believe mentions that the difference b/w ...A and A... is that the first one does Left side expansion and the second one does right side expansion. I am not sure what that means. Could anyone please clarify this with how something would look like when expanded. The only thing I understand so far regarding dots on the right hand side are the examples such as this

//Foo and bar are variadic parameter packs
Foo...                     => Foo1, Foo2, Foo3, etc
std::vector<Foo>...        => std::vector<Foo1>, std::vector<Foo2>, std::vector<Foo3>, etc.
std::tuple<Foo...>(bar...) => std::tuple<Foo1, Foo2, Foo3, etc>(bar1, bar2, bar3, etc)
&bar...                    => &bar1, &bar2, &bar3, etc

could any one please clarify what the dots expand to in line 1 and line 2 and what is the difference between left side expansion and right side expansion ?