All characters have six basic statistics:

* Strength (STR): Strength is a measure of muscle, endurance and stamina combined. Strength affects the ability of characters to lift and carry weights, melee attack rolls, damage rolls (for both melee and ranged weapons,) the Jump, Climb, and Swim skills, several combat actions, and general checks involving moving or breaking stubborn objects.
* Dexterity (DEX): Dexterity encompasses a number of physical attributes including hand-eye coordination, agility, reflexes, fine motor skills, balance and speed of movement; a high dexterity score indicates superiority in all these attributes. Dexterity affects characters with regard to initiative in combat, ranged attack rolls, Armor Class, Reflex saves, and the Balance, Escape Artist, Hide, Move Silently, Open Lock, Ride, Sleight of Hand, Tumble, and Use Rope skills. It also affects the number of additional attacks of opportunity granted by the Combat Reflexes feat. Dexterity is the ability most influenced by outside influences (such as armor).
* Constitution (CON): Constitution is a term which encompasses the character's physique, toughness, health and resistance to disease and poison. The higher a character's Constitution, the more hit points that character will have. Constitution also is important for Fortitude saves, the Concentration skill, and fatigue-based general checks. Constitution also determines the length of a barbarian's rage. Unlike the other ability scores, which render the character unconscious or immobile when they hit 0, having 0 Constitution is fatal.
* Intelligence (INT): Intelligence is similar to IQ, but also includes mnemonic ability, reasoning and learning ability outside those measured by the written word. Intelligence dictates the number of languages a character can learn, and it influences the number of spells a preparation-based arcane spellcaster (like a Wizard) may cast per day, and the effectiveness of said spells. It also affects how many skill points a character gains per level, the Appraise, Craft, Decipher Script, Disable Device, Forgery, Knowledge, Search, and Spellcraft skills, and bardic knowledge checks.
* Wisdom (WIS): Wisdom is a composite term for the characters enlightenment, judgement, wile, willpower and intuitiveness. Wisdom influences the number of spells a divine spellcaster (like clerics, druids, paladins, and rangers) can cast per day, and the effectiveness of said spells. It also affects Will saving throws, the Heal, Listen, Profession, Sense Motive, Spot, and Survival skills, the effectiveness of the Stunning Fist feat, and a monk's quivering palm attack.
* Charisma (CHA): Charisma is the measure of the character's combined physical attractiveness, persuasiveness, and personal magnetism. A generally non-beautiful character can have a very high charisma due to strong measures of the other two aspects of charisma. Charisma influences how many spells spontaneous arcane spellcasters (like sorcerers and bards) can cast per day, and the effectiveness of said spells. It also affects Bluff, Diplomacy, Disguise, Gather Information, Handle Animal, Intimidate, Perform, and Use Magic Device checks, how often and how effectively clerics and paladins can turn undead, the wild empathy of druids and rangers, and a paladin's lay on hands ability.

An ability score is a natural number, with a value of 10 or 11 representing average human ability.

Determining ability scores

There are several methods of determining a character’s initial ability scores during character creation:

* Rolling dice (3d6): This is the standard method for some pre-3.0 editions. For each ability score, the player rolls 3d6, and adds the values, resulting in scores ranging from three to eighteen, averaging between 10 and 11.
* Rolling dice (4d6k3): This is the standard method for 3.0 and 3.5 editions.[1] For each ability score, the player rolls 4d6, and adds the three highest values, resulting in scores ranging from three to eighteen, skewed towards higher numbers, averaging 12.24, though the most probable result is 13[2]
* Predetermined array of scores: Less random, but inflexible.
* Point buy: In the point buy system, a player has a certain number of points to spend on their ability scores. The more powerful the characters are intended to be, the more points will be available to the players. (Characters are usually more powerful for a more difficult game.) Possible ability scores range from eight to eighteen, and each score has a certain point cost affixed to it, where higher scores tend to cost more points per level than lower ones. This method is used in Dungeons & Dragons Online (and other computerized D&D-based games, such as Neverwinter Nights) to avoid imbalanced characters getting an unfair advantage over other players.

Taken from Wikipedia