Hmmmm. This article seems to be a good effort, but it is not entirely accurate. For example, the terms “sidechain” and “Plasma” are not used to refer to the same thing. A “sidechain” means that there is another chain with its own independent consensus mechanism, but that you can move tokens across in some fashion where failure of the sidechain limits the damage to only the tokens which were actually on the sidechain. On Plasma, by comparison, the failure of the additional “Plasma chain” does not lose any tokens, provided that the main chain is still secure. This is because the consensus rules of the Plasma chain depend on the main chain rather than being independent. They are not “side to side” and connected. They are more like “parent and child” where one has the ultimate authority no matter what the other one does. To make it more clear: the users of a Plasma chain must watch both the Plasma chain they are using as well as the main chain it depends upon to remain safe. But the users of the main chain can ignore the Plasma chain. On a sidechain users from both chains can ignore the other chain for most purposes, so it truly is a “side to side” relationship. Does my description make sense?