I recently read a review about Return to Ravnica and the reviewer says that, for example, Temple Garden is way better than Selesnya Guildgate. Can someone point out the reasons behind that? Additionally, why is Temple Garden called a Shockland?
Shocklands (which allow you to "Shock" yourself in order to get an untapped land) have many advantages:
- Good color depth without loss of tempo. Oftentimes, getting your land into play untapped is worth two life; shocklands give you the option to set that up.
- Excellent color-fixing with fetch effects.
- The synergy between shocklands and fetchlands is what makes Modern mana bases so strong. I can crack a Misty Rainforest and get any of these color combinations: W/G, W/U, U/B, U/R, U/G, B/G, R/G. See this answer for more information about the shocks + fetches style of mana base.
- We can have four- and five-color decks in Innistrad/RTR Standard thanks to Farseek's ability to fetch any of the ten shocklands.
- Shocklands interact positively with other cards that care about basic land types as well. In particular:
- Shocks power up M13 and Innistrad "buddy" lands (like Sunpetal Grove), which require you to have lands of specific basic land types in play. In a three-color deck, a single shock in play is sufficient to make every single one of your "buddy" lands enter play untapped.
- Shocklands have powerful synergy with "Kird Ape" creatures like Wild Nacatl (which was once banned from Modern for being too consistent of a 3/3 on turn 2) and Flinthoof Boar (which saw tournament play in Standard Gruul decks).
Flexibility. If you choose to have the land enter tapped, then the cards are no different, but only Temple Garden gives you any choice at all. The difference from being able to use that mana on the turn that you play it may amount to less life lost than the 2 you pay to have it enter untapped.
Shock was the quintessential burn spell for a while when WotC thought that Lightning Bolt was too quick and powerful. Shock was released in multiple base sets, and since it deals 2 damage, people called the cycle of lands that deal 2 damage to you Shocklands.
Adding to user1873's existing answer: as you say, the fact that Shocklands have the same land types as basic lands (e.g. "Forest Plains") is huge. It means you can fetch them up with Fetchlands, or any other spell that looks for a Forest or a Plains (though not of course "a basic Forest", or "a basic Plains').
A manabase judiciously combining both Fetchlands and Shocklands is pretty close to the ultimate way of having the right colour of mana available exactly when you need it, in a 3+ colour deck. And if you're using fetches to get your Shocklands at the end of your opponent's turn, the "comes into play tapped" restriction isn't even a drawback, at that point.
Shock lands get their name because of the spell "Shock", which deals 2 damage to target creature or player. With the shock lands, in order to get them into play untapped, you have to hit yourself with a shock. Shock lands are so expensive becuase of mana fixing. Anything that is invunerable (lands are the hardest thing in MTG to kill, except emblems) and can help you get the colors you need to the battlefield, will be worth a good portion of money. The cost is increased as well becuase of the shock lands' synergy with the "fetch lands". These are lands that can grab other lands. The shock lands are the only nonbasic lands with basic land types in their card type, so they are the only non-baic land that the fetch lands can fetch you.