Wizards of the Coast defines these terms as follows:
Playtest card — A card (typically a basic land) marked with the name of another Magic card for the purpose of playtesting. Playtest cards aren't trying to be reproductions of real Magic cards; they don't have official art and they wouldn't pass even as the real thing even under the most cursory glance.
Proxy card — A placeholder card assigned by a judge during an event to replace a card that was damaged during the event to be used during that event only.
Counterfeit card — An inauthentic Magic card made to pass as, or represent, an existing authentic Magic card. Counterfeit Magic cards will often use Wizard’s registered trademarks, logos, card mechanics, card names, and artwork.
Sanctioned event — Any Magic event hosted by a WPN store or approved tournament organizer that is organized in Wizards EventLink. Sanctioned events require players to register using a Wizards Account or guest account, will be visible in our Store and Event Locator, and will contribute towards your store’s WPN play metrics.
Unsanctioned event — Any Magic event that is not organized in Wizards EventLink. These events are not directly connected to the WPN play system, will not be visible in our Store and Event Locator, cannot use WPN promotional materials, and will not contribute towards your store’s WPN play metrics.