As for what it does, thats hard to tell because it literally doesnt tell you
However, you can always use cards with cycling like Lrien Revealed at the end of your opponents turn to fetch a card, and, more importantly, exile the card on top of your library to play it on your turn with no restriction
Secret Rendezvous
Some of the best cards that work with Vial Smasher include those that add extra damage for your spells, like: Angrath's Marauders Guttersnipe Solphim, Mayhem Dominus 5 General Kreat, The Boltbringer A Powerhouse In The Command Zone A lot of Goblin decks revolve around getting out a ton of tokens or by dealing tiny amounts of damage either all at once or over the course of the game
All those Magic players, drawing their cards, slinging their spells
Example two: Our cunning opponent attacks us with a Minotaur Aggressor, we block with a Bear enchanted with Bear Umbra