The blue links that you see on a card's profile will explain the Trait(s) the card has. You will find that the Rare and better Cards will have multiple Traits. Below is a list of the various Traits and what they are capable of doing.
Afterlife:
When this is destroyed, you can play it a second time
Amphibious:
Play on Water or Land.
Anti-Hero (x):
(x) Strength against Heroes.
Armoured (x):
Reduce damage to this by (x).
Bounce:
Put it back in its owner’s hand.
Bullseye:
Doesn’t charge the opponent’s Block Meter.
Deadly:
Destroy any Plant this hurts.
Freeze:
That Zombie skips its next attack.
Frenzy:
When this destroys a Plant, it attacks again.
Gravestone:
Hides in a Gravestone until its time for Tricks.
Splash Damage (x):
When this attacks, it also deals (x) damage to Zombies next door.
Strikethrough:
Hits the Zombie here and the Zombie Hero.
Team-Up:
You can fit two Plants here.