Application pool is created the each and every website.
Application domain is created to one domain purpose.

IIS process is w3wp;

Every application pool in IIS use it's own process; 
AppPool1 uses process 3784, AppPool2 uses process 5044
Different applications in Asp.net will use different 
AppDomain; 

AppTest2 and AppTest2 are in different AppDomain, but in 
the same process.
 
What's the point to use them?
 
Application pool and AppDomain , both of them can provide 
isolations, but use different approches. Application pool 
use the process to isolate the applications which works 
without .NET.  But AppDomain is another isolation methods 
provided by .NET.
If your server host thousands of web sites, you wont use 
thousands of the application pool to isolate the web sites, 
just becuase, too many processes running will kill the os. 
However, sometime you need application pool. One of the 
advantages for application pool is that you can config the 
identity for application pool. Also you have more flexible 
options to recyle the application pool. At least right now, 
IIS didnt provide explicit options to recyle the appdomain.

There are different way to deploy the web application in 
web server like
1- X Copy deployment
2- create setup package and install the server machine
3- use the deployment tools and configure the server 
repositery and drag and drop all files in your machine to 
virtul folder of server machine,

if you really want to d that so just sit in front of system 
and say..."INSTALL" . it will automatically install on your 
system..no matter either web or window.

create new vertual directory 
create new webside in directory
give the path for webside 
set port and security

If you are running your IIS server with 2 different 
versions of framework(1.1 & 2.0)you can create 2 different 
application pools and point your application to the 
required framework you want to run.

yes it is correct The problem might be a application pool
will be associated with 2 different application that uses
different frameworks.

Try using 3rd party utilities such as unformat,Uneraser ..
you may be able to recover some % of data depending on how
lucky you are on the day when you know that your day started
off with hard drive formatted..

But if you really want to get some data out of your
formatted hard drive.. better spend some money and get data
retrieved from Data Recovery Specialist... While they
wouldn't guarantee you 100% recovery .. but will do happily
for money..

There are several kinds of third party tool. Which will 
really help to retrive the formated data...

The new request-processing architecture and application 
isolation environment enables individual Web applications, 
which always run in user mode, to function within a self-
contained worker process. A worker process is user-mode 
code whose role is to process requests, such as returning a 
static page or invoking an Internet Server API (ISAPI) 
extension or filter. Worker processes use HTTP.sys to 
receive requests and send responses over HTTP.

IIs 6.0 architecture is based on Http.sys kernel and 
metabase configuration is in xml format security features 
all are same like iis5.0 but passport support included in 
6.0