How use Group Policy and Login Script To implement TMG Client?

Hi,

I read That for apply TMG client from GPO , First from this path:"user configuration"-> "policies" -> "windows settings" -> "internet explorer maintenance" -> "connection" -> "automatic browser configuration"

should enable "enable automatic configuration" check box  and after in the field named "automatic proxy URL", write the URL provided by your proxy server for accessing the .pac file

SO I have 2 Question :

1)what is.PAC file?i mean how i should create it or How I find it?   

2)as TMG install in local server(not Domain) I must access GPO from MMC  is it true?

3)in field name automatic proxy URL  if i type my URL is it enough to implement tmg client through GPO?and is it true  like this url

http://tmg1.xyzw.com:8080/