if u do a project in.net you have many webforms.each form 
should connect with database.so u have to write 
connectionstrings in each form.u can avoid these things.u 
can declare connection strings in global wise.then it will 
inherit in each form

u can declare ur database connection in connection string
and u can declare all ur application settings in appsettings
like ur service url etc

<appsettings> is used before connection string
we use it to set the applicstion setting so that program 
run successfully,but 
<connectionstring> is used to make the or establish the 
connection.