Fixes #427

02_getting_started.asciidoc

@@ -370,7 +370,7 @@ image:images/bob-cafe-posapp.png[]
 
 ==== A Lightning Invoice
 
-Alice selects the "Cafe Latte" option from the screen and is presented with a _Lightning Invoice_ as shown in <<bob-cafe-invoice>>
+Alice selects the "Cafe Latte" option from the screen and is presented with a _Lightning Invoice_ (also known as a "payment request") as shown in <<bob-cafe-invoice>>
 
 [[bob-cafe-invoice]]
 .Lightning Invoice for Alice's latte
@@ -382,6 +382,11 @@ To pay the invoice, Alice opens her Eclair wallet and selects the "Send" button
 .Alice Send
 image:images/alice-send-start.png[width=300]
 
+[TIP]
+====
+The term "payment request" can refer to a Bitcoin payment request or a Lightning invoice and the terms "invoice" and "payment request" are often used interchangeably. The correct technical term is "Lightning invoice", regardless of how it is named in the wallet.
+====
+
 Alice selects the option to "scan a payment request" and scans the QR code displayed on the screen of the tablet (see <<bob-cafe-invoice>>), and is prompted to confirm her payment, as shown in <<alice-send-detail>>:
 
 [[alice-send-detail]]