Cards

Individual cards are at the heart of Magic.  Knowing how to read cards and identify the common types is important.  This page assumes you've read the Intro first.

Reading cards

The official site has a good primer on how to read a Magic card.

from the official site

Most of the card components are intuitive from the above picture:

• Name: name of card
• Mana cost: the number and color of mana required to play the card
• Illustration: art that has no bearing on the game
• Type line: the type of card it is (see next section); sub-types are listed here, where applicable, after a long dash
• Expansion symbol: identifies rarity and set the card came from
• Text box: provides additional information (normal type) and flavor text (italics)
• Power/toughness: for creatures only. Power = the amount of damage it can deal in a turn.  Toughness = the amount of damage in a turn it must receive to kill it.

Types of cards

Magic has a number of basic card types you need to understand: land, creature, enchantment, planeswalker, artifact, sorcery, and instant,.  The first five types are permanents- they are put on the battlefield when they're cast and remain there until removed by combat or card effect.  The last two (sorceries and instants) are not: once their effect is resolved, the card is put in the graveyard.

Cards have types, and some have subtypes.  Anything after a long dash is a subtype.

Land

Land cards generate mana you need to pay for spells.  They can be played only on your turn (during your main phases).  You can play only one land per turn.

Lands can be used once per turn (including the turn they come into play) by tapping them.  When you tap a land, you add one mana of a color that land can produce to your mana pool.  There are basic and non-basic lands.

Basic lands: plains, island, swamp, mountain, forest

Non-basic lands: many examples, some of which are shown below

The basic lands are straightforward: tap a plains to add one white mana, tap a forest to add one green, etc. The non-basic lands are a little trickier, but still not bad.  Take Wind-Scarred Crag.  It enters the battlefield tapped (so you can't use it right away), you gain one life, and on your next turn, you can tap it to add one red or one white mana.  Tournament Grounds is very flexible if you're playing a deck with a lot of Knight creature cards, but only good for one colorless mana otherwise.

Key to deck building is including the right quantity and type of lands in your deck.

Lands are free to play; the remaining card types are played by paying their mana cost, in the upper right corner.

Creature
Creatures are what you can use to attack and block.  They can be played only on your turn (during your main phases) unless they have the 'flash' keyword. They cannot attack or tap the turn they come into play unless they have the 'haste' keyword. Their power (first number in the lower right) is the amount of damage they deal when they attack or block.  Their toughness (second number) is the amount of damage it takes to kill them in one turn. Take Sporecap Spider below.  If he takes 5 damage in a turn, he dies (is put in the graveyard), but if he takes only 4 damage, at the end of the turn all of that is removed.  When creatures receive damage greater than or equal to their toughness, or their toughness is somehow reduced to 0, they are put in the graveyard.

Creatures tap to attack, and only untapped creatures can block.

Creatures have subtypes, or creature types, that I explain more here.

Sorcery

Sorcery cards are spells that can be used only on your turn (during your main phases).  Once their effect is resolved, the card is put in the graveyard.

Instant

Instant cards are spells that can be used on anyone's turn, and in any phase (not just main phases).  Once their effect is resolved, the card is put in the graveyard.  

Being able to play cards in any phase is powerful- more on this another time.

Enchantment

Enchantments alter the state of the game, generally by giving you (or your permanents) a boost or hurting your opponent.  They can be played only on your turn (during your main phases) unless they have the 'flash' keyword. Enchantments can go on the battlefield like creatures, or attach to permanents if they're "auras."  If auras, it will tell you what type of permanent it enchants.

If a permanent is destroyed, any auras attached to that permanent go in the graveyard.

Planeswalker

Planeswalkers are powerful beings that fight on your side (technically, in Magic, you are a planeswalker). They can be played only on your turn (during your main phases).  Planeswalkers have a starting loyalty (lower right corner), and each turn (including the turn they come into play) they can use one of their abilities by adding or subtracting the loyalty indicated by each.  When players attack an opponent who has a planeswalker on the battlefield, the attacker must declare which of his creatures is attacking the player, and which the planeswalker(s).  Damage done to planeswalkers reduces their loyalty (e.g. 3 damage would remove 3 loyalty).  Planeswalkers are put in the graveyard when their loyalty reaches 0.

Artifact

Artifacts are powerful objects.  They can be colored or colorless (determined by their mana cost).  They can be played only on your turn (during your main phases) unless they have the 'flash' keyword.   Artifacts can tap the turn they come into play (unless they're creatures- some artifacts are also creatures.  Those follow the rules for creatures mentioned above).  Some artifacts have an equipment subtype.

Artifacts that are equipment are played like normal cards (pay their mana cost during your main phases). But they also have an 'equip' cost listed on the card: the cost to attach it to a creature.  If a creature would be destroyed, the equipment stays on the battlefield and can be equipped to another creature.
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Those are the card types in a nutshell.  As I build out the site, I'll add posts relevant to cards to discuss:
- how and where to search for cards
- judging a card's value