Setting async to false means that the statement you are calling has to complete before the next statement in your function can be called. If you set async: true then that statement will begin it's execution and the next statement will be called regardless of whether the async statement has completed yet.
$( function () {
$( "button" ).click( function () {
var car = { Make: 'Audi', Model: 'A4 Avant', Colour: 'Black', Registered: 2013 };
$.ajax( {
type: "POST",
url: "/Receiver",
data: car,
async:false,
datatype: "html",
success: function ( data ) {
$( '#result' ).html( data );
}
} );
} );
} );
By default async is true in ajax call.