CH02::Change update for illustration, add detail

- Update text to refer to new illustration

- Introduce the term "change output" in addition to existing term
  "change address"

- Add information about the privacy advantages of unique change
  addresses

ch02.asciidoc

@@ -253,22 +253,33 @@ that's what the protocol itself uses.
 ==== Making Change
 
 ((("change, making")))((("change addresses")))((("addresses", "change
-addresses")))Many bitcoin transactions will include outputs that
-reference both an address of the new owner and an address of the current
-owner, called the _change_ address. This is because transaction inputs,
+addresses")))In addition one or more outputs that pay the receiver of
+bitcoins, many tranactions will also include an output that pays the
+spender of the bitcoins, called a _change_ output.
+This is because transaction inputs,
 like currency notes, cannot be divided. If you purchase a $5 US dollar
-item in a store but use a $20 US dollar bill to pay for the item, you
-expect to receive $15 US dollars in change. The same concept applies to
+item in a store but use a $20 dollar bill to pay for the item, you
+expect to receive $15 dollars in change. The same concept applies to
 bitcoin transaction inputs. If you purchased an item that costs 5
-bitcoin but only had a 20 bitcoin input to use, you would send one
-output of 5 bitcoin to the store owner and one output of 15 bitcoin back
-to yourself as change (less any applicable transaction fee).
-Importantly, the change address does not have to be the same address as
-that of the input and for privacy reasons is often a new address from
-the owner's wallet.
 
 Different wallets may use different strategies when aggregating inputs
 to make a payment requested by the user. They might aggregate many small
+bitcoins but only had an input worth 20 bitcoins to use, you would send one
+output of 5 bitcoins to the store owner and one output of 15 bitcoins back
+to yourself as change (not counting your transaction fee).
+
+At the level of the Bitcoin protocol, there is no difference between a
+change output (and the address it pays, called a _change address_) and a
+payment output.
+
+Importantly, the change address does not have to be the
+same address as that of the input and for privacy reasons is often a new
+address from the owner's wallet.  In ideal circumstances, the two
+different uses of outputs both use never-before-been addresses and
+otherwise look identical, preventing any third party from determining
+which outputs are change and which are payments.  However, for
+illustration purposes, we've added shading to the change outputs in
+<<transaction-chain>>.
 inputs, or use one that is equal to or larger than the desired payment.
 Unless the wallet can aggregate inputs in such a way to exactly match
 the desired payment plus transaction fees, the wallet will need to