[Havent_a_clue]

I'm currently working on a project and came across this piece of code. Unfortunately, as my user name suggests, i don't know whats going on. Could anybody help???
thanks in advance...

function flip(pic, r)
{
if(r == 2)
{
source = eval(pic + "2.src");
document[pic].src = source;
}
if(r == 1)
{
source = eval(pic + "1.src");
document[pic].src = source;
}
}

function link()
{
}