"Oversize cards" is not a "set" by the usual Magic definition, but I'd guess your online store categorizes them that way to make it clearer to customers they're buying an abnormal card
This five-mana instant reveals the top card from your library, you draw it, and then lose life equal to its mana value
Commander is more interesting when players shake things up, play outside the meta, and introduce their own cool tech
In the case of any of the five lands in this release, you'll be able to play it only during your main phase while the stack is empty and only if you have an available land play remaining
All the copies of the card went home with Wizards of the Coast employees, who held onto them and occasionally teased fans by showing them off at public events
Not that Magic: The Gathering cards can be valuable, that's long-established, but that a single card could ever be worth half-a-million dollars plus change