What is a function parameter =[] for?

[fl]

Hi,

I have tried the below function and find that it can remember the previous
setting value to 'val'. I think the second parameter has something on this 
effect, but I don't know the name and function of '=[]' in this application.

Could you explain a little to me?
Thanks,


def eList(val, list0=[]):
    list0.append(val)
    return list0
list1 = eList(12)
list1 = eList('a')