Merge pull request #853 from rating89us/patch-60

ch10: candidate blocks -> winning/valid blocks; some other fixes

ch10.asciidoc

@@ -781,7 +781,7 @@ In the first diagram (<<fork1>>), the network has a unified perspective of the b
 .Before the fork&#x2014;all nodes have the same perspective
 image::images/mbc2_1002.png["Before the fork - all nodes have the same perspective"]
 
-A "fork" occurs whenever there are two candidate blocks competing to form the longest blockchain. This occurs under normal conditions whenever two miners solve the Proof-of-Work algorithm within a short period of time from each other. As both miners discover a solution for their respective candidate blocks, they immediately broadcast their own "winning" block to their immediate neighbors who begin propagating the block across the network. Each node that receives a valid block will incorporate it into its blockchain, extending the blockchain by one block. If that node later sees another candidate block extending the same parent, it connects the second candidate on a secondary chain. As a result, some nodes will "see" one candidate block first, while other nodes will see the other candidate block and two competing versions of the blockchain will emerge.
+A "fork" occurs whenever there are two different valid blocks at the same block height competing to form the longest blockchain. This occurs under normal conditions whenever two miners solve the Proof-of-Work algorithm within a short period of time from each other. As both miners discover a solution for their respective candidate blocks, they immediately broadcast their own "winning" block to their immediate neighbors who begin propagating the block across the network. Each node that receives a valid block will incorporate it into its blockchain, extending the blockchain by one block. If that node later sees another valid block extending the same parent (at the same block height), it connects the second block on a secondary chain, forking its main chain. As a result, some nodes will "see" one winning block first, while other nodes will see the other winning block first, and two competing versions of the blockchain will emerge.
 
 In <<fork2>>, we see two miners (Node X and Node Y) who mine two different blocks almost simultaneously. Both of these blocks are children of the star block, and extend the chain by building on top of the star block. To help us track it, one is visualized as a triangle block originating from Node X, and the other is shown as an upside-down triangle block originating from Node Y.