difference between "IS" and "AS"

"IS" keyword can be used to check whether two variables are of same type.

Ex:
object obj="narendra";
object obj1=1234;

if(obj is string)
{
Console.WriteLine("Success");//this statement executes as obj is string
}

if(obj1 is string){
Console.WriteLine("Success");//this statement is not executed as obj1 is not string
}

"AS" keyword is used to convert variables from one type to another and if conversion is not successful then null is stored.

string str=obj as string;//here it succeeds and str has value of "narendra"

string str1=obj1 as string;// here it fails and str1 has null value