I first started playing Magic around the time of Worldwake, which really set me off on the path of being a casual player (thanks, Jace, the Mind Sculptor for being my first-ever introduction to FNM). The playgroup I was in ran several tribal decks (elves, vampires, and even myr), and when I saw the impressive power behind pumping an entire board to obscene numbers, it got me hooked.
In a nutshell, tribal strategies take a single creature type and construct a deck that buffs and synergizes around that type.
The Tribal Cards
Mayor of Avabruck
I'm pretty sure Wizards misprinted this card or something, because this guy is ridiculous for only 2cmc. Pumps your weak Humans for some early minor threats, but the transformed side is bigger, badder, and creates 3/3s at the end of your turn.
Kruin Outlaw
While the front is rather unimpressive, flipping this with even only 2 other Werewolves is usually GG. This deck has a lot of lord effects but not a ton of evasion, so giving your entire team menace is very relevant. Also, double strike is sexy.
Moonlight Hunt Unless you're in a terrible board state or the creature you're targeting has a particularly high amount of toughness, this basically reads as a green tribal Doom Blade. I can frequently pull 6-8 damage with this because of all the lord pumps on my board.