google_ad_slot what does this mean?

whats does this google ad slot means and what is the difference between this and the old Code?..

<script type='text/javascript'><!--
google_ad_client = 'pub-XXXXXXXXXXXXXXXX';
google_ad_slot = '6051019620';
google_ad_width = 250;
google_ad_height = 250;
//-->
</script>
<script type='text/javascript'
src='http://pagead2.googlesyndication.com/pagead/show_ads.js'>
</script>

 

I think it's useful for the manage ads feature. It's used by Google to identify the ad spot so it reflects the changes you make in the Manage Ads tab.

 

Something like unique number which contain your channel, colors.

 

on the old code its used to be ad channel, now on the new code its ad slot. pretty much same thing but one good thing is that you were not able to edit your ad channel before and would have to create a new channel if you needed to update the code. now with the new code, ad slot is just like the channel but it allows to to update/modity and keeps a record of your code for your future reference which is good

 

i think maybe its a settings saved in the adsense server..
google old adsense code looks like this;

<script type="text/javascript"><!--
google_ad_client = "pub-XXXXXXXXXXXXXXX";
google_ad_width = 728;
google_ad_height = 90;
google_ad_format = "728x90_as";
google_ad_type = "text";

google_ad_channel = "your_ad_channel";
google_color_border = "FFFFFF";
google_color_bg = "FFFFFF";
google_color_link = "0000FF";
google_color_text = "000000";
google_color_url = "008000";
//--></script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

 

it is the channel you select during making ads.

If no channel selected then default