The goblin deck is an aggro deck with creatures containing the creature type goblin. Goblin decks are very fast, most are mono red but there are variants that splash black for cards like Patriarch's Bidding and other control cards such as Cabal Therapy. Goblin decks want to win the game early on, hence most of the cards in a goblin deck cost 1-3 mana with some exceptions such as Kiki-Jiki, Mirror Breaker and Siege-Gang Commander at 5 mana. Goblin decks utilize cards such as Goblin Warchief, Goblin Piledriver and Skirk Prospector to the max.
A goblin deck can play something like this: Turn 1 mountain and Skirk Prospector, turn 2 play a mountain, sacrifice Skirk Prospector and cast Goblin Warchief and attack. Turn 3 maybe drop another mountain drop Goblin Piledriver and maybe something else and attack for a lot of damage.
Or something Like this:
turn 1 Mountain, Goblin Guide attack with goblin Guide =2damage
turn 2 Mountain, 2 Goblin Guides, attack with all =4damage, already did 2, so enemy is on 14. turn3 mountain Goblin Chieftain, attack with al=8damage, already did 6, so enemy is on 8. turn4 Attack, 2 Goblin grenade, Fodder Launch+Lightning bolt, 3 Lightning bolts or something else and your enemy is dead.
Goblin decks are very powerful and tend to be very fast most of the time. They aren't very easy to play because there are a variety of decisions that a player must to make with goblin decks during different scenarios to utilize their goblins to the best of their ability.
During Worlds 2006, another Goblin variant nicknamed Dirty Kitty emerged onto the scene. This version splashed green for Fecundity and used Mogg War Marshal and Empty the Warrens to turn Skirk Prospector into a mana-producing card-drawing engine. This should boost the storm count for Empty the Warrens which should generate a deadly horde of Goblins when combined with Goblin Warchief and Goblin Piledriver. Alternatively, either Grapeshot or Goblin Sharpshooter could deal lethal direct damage.