Help With map() *He says while pulling his hair out*

[EricIDLE]

Ok first off I have a wee problem with one of the examples in my book it is
as follows:

s="12.19.6.7.12"
ls = string.split(s, '.')
md = map(string.atoi, ls)

Ok. well the problem is basically the whole thing. I know s="12.19.6.7.12"
is just defining the varible 's' with the numbers. But my first problem is
after string.split in its argument I know what the S means but I dont know
what the '.' means does that mean to remove all the periods?
The second problem is that I dont quite grasp the map() function what
exactly does it do, In its argument it says in lamens terms "Turn the string
ls into intergers" my problems is wasent it always intergers? I mean the
varible ls contains ['12', '19', '6', '7', '12'] arent those intergers they
are numbers. Any ways if you could reply answering all the questions in
whole or maybe just a few of em' it would be great.

Thanks.