Sure.
Its primary function is that it reveals the matching card and its neighbors in a Hidden game (where you cannot see your opponent's cards). How many cards you reveal depends on the rarity of the card you played. If yours was Common, you'll reveal the card across from yours and the one card on each side of it. (If you play from one of your edges, position 1 or 8, it only reveals the one neighbor with it, it doesn't wrap around to the other side of the hand.) Playing an Uncommon reveals two neighbors on each side for a possible five cards altogether. A Rare Far Sight will reveal every card in the opponent's hand.
Additionally, if the matching card (the one across from yours) is already revealed or if you weren't playing a Hidden match to begin with, there is an added effect. (You'll still reveal the card's neighbors, if applicable.) The bonus depends on the color of YOUR OPPONENT'S matching card (the kind of resources it costs.) If it is red/bricks, you'll gain some Tower; if blue/gems, you'll gain Tokens; if green/recruits, you'll gain Wall; if multicost, you'll gain Stock; if 0-cost, no bonus. The amount of Tower/Tokens/Wall/Stock you gain depends on the rarity of the card you played, less for Common and most for Rare. (Again, you're looking at the opponent's card's COLOR, but your card's RARITY to predict the effect.)
You can tell which of your own cards are revealed to your opponent because there will be a blue icon of a eye next to the card, similar to the "New" icon. Cards remain revealed until played or discarded (or shuffled by card effect, which is functionally a discard effect).