@Galenbeta: try learning to read.
I mean, seriously.
What the hell is wrong with you?
@Galenbeta: Then i assume you are blind if you can't see this:
Yukari has trained Martial Arts since she was six. Even though she is by no means a master of it she has enough knowledge to compete with people that train something like that. She just an average girl in physical build, the only thing that is vastly above the average human being her intelligence. She makes up for the lack of physical attributes with Magic and Tracing. The first and most obvious example in Magic is her Reinforcement ability, which is used to make objects stronger, more durable and simply better. A lamp will burn brighter, a sword will be sharper and a mount will be faster. It's the most basic magic known by all Magi. All of them use it on their own body most often. It gives them the speed to fight with superhuman enemies and supernatural creatures far beyond the human limit. Their bodies become harder than steel and they gain enough strength to punch chunks out of concrete. The other basic ability is alteration, allowing to change the form of something. A simple tree branch can be made into a fine arrow and bow, a lump of metal becomes a sword and so on, it's rarely used by Yukari in combat as she has better means of attacking. For that purpose she often prepares many gems with heat stored in them to use them later in combat.
Yukari being a Contractor can make contracts with various Spirits. The contract is made by touching an item or artifact related to the Spirit in question. The Spirits don't even have to be real. They can range from people from history, over those from myths, folklore and legends all the way to characters from famous works of fiction or even heroes from the future or even powerful persons from the history that were never recorded. Once the contract is made the Spirits are called Servants and will be bound to the personal Spiritual Plane of the Contractor. A Spiritual Plane is a virtually endless pocket dimension in which the Spirits can rest when not summoned, it's often an item in the possession of the Contractor. In Yukari's case it's her pendant that serves as a Spiritual Plane. The inside appearance of it can be completely change whenever the Servants desire and they are free to even create entire cities with imaginary people in them (though it's rare for them to do so as they are still aware that the beings are fake and thus they can't enjoy that kind of life inside the Plane). Though they are Spirits, once summoned from the Spiritual Plane into the real world they get semi-real bodies of blood and flesh. They are real as in that they bleed just like any living being would but still Spirits in the regard that even if they are killed they don't die. Instead they just return to the Spiritual Plane where they rest and regenerate for a certain amount of time. If a Contractor dies all of his Servants will vanish as well and return to the afterlife, though they can be summoned again if another Contractor finds an item related to them. A rule between Contractors is that if they are defeated in a match one of their Servants will be taken by the victor. One can also give their Servants to other Contractors with their own free will, though many would rather die than to do that. The main motivation for Servants to serve their Contractor is that if their Master gets the Holy Grail, they will also be granted a new life. Their body will rise from the afterlife and they will live as humans again. They can chose to live in their own time period again in a different universe or even to change things from the past. The Contractor will still have the Servant as that was never the real body to begin with but just an exact copy of it, a Spirit, so the Master won't even notice a change. Despite all of that there are still Servants that are difficult to deal with simply because of their personalities contradict that of their Master to a great degree. While they have to obey to command of their Contractor they have a free will and they are free to do anything as long as their Contractor does not forbid it directly. Most Contractors only can summon one Servant to the world at a time, while the next level the Master can summon from two to even all of his Servants at once. To become a Master one would either have to participate in the Holy Grail War (though most chose already are Master) or take a special trial after they possess a certain amount of Servants. There is also the so called Potential system but it's so rare that there is no current info on it.
A power unique to Contractors that makes them so powerful when compared to other Magi even without the direct summoning of Servants is Tracing. Tracing is the power of Contractors to call upon the weapon or other piece equipment belonging to one their Servants. While using the weapon they get stats close to that of the Servant as well as a fraction of their skill and knowledge when using the weapon. This makes Contractors very dangerous foes even without the need to summon one of their Servants. Besides the weapon, physical attributes and skill Contractor's will also have their clothes altered to a certain degree. Those with a weak mind and that have just become a Contractor will have their personality altered to be closer to that of the Servant who's weapon they are using, sometimes completely falling under the control and influence of the weapon. Yukari has managed to completely seal off any effect on her mind, but her appearance still changes. Those who are high level Masters are completely immune and their personality and appearance will only change if they allow it. And their stats and skills also reach the level of their Servant allowing the Masters to become the heroes themselves but still keeping their own abilities, knowledge and experiences making them extremely powerful.
As of now Yukari only has two Servants, something which can be considered low. She can only summon one at a time.
But i will admit it's pretty hard to spot given how tiny it is.
First of all, let's all take a deep breath and calm down.
@Galenbeta: It doesnt matter you were trolling or not, please apply water to the multitude of burns you received.
@SamJaz: Loved the Nostalgia Critic video, I didnt like the AVGN comparison, that guy is a good guy in real life, Galen is more like the Irate Gamer (http://knowyourmeme.com/memes/people/the-irate-gamer)
@Fehafare: Dont feed the troll, you shouldnt care what he says, you know he is either trolling, ignoring the rules or better yet completly oblivious to how the world works. Consider this, I'm one of the most rabid anti-non original content on the site and I'm trying not to go ballistic, so let's all take a deep breath and calm down.