The six different hands associated with the Buddha are:
Touching the earth - the right hand rests on the right thigh with the fingers pointing downwards and touching the earth the left hand rests in the Buddha's lap. This mudrā is frequently called "calling the earth to witness” - the gesture symbolises the Buddha's renunciation of worldly desires, and as this is the central moral precept of Buddhism is by far the most common depiction.
Meditation – both of the hands are shown lying flat in the Buddha's lap, palms displayed upwards. This mudrā is usually associated with a seated Buddha. It shows that the Buddha is disciplining his mind through deep meditation, a necessary step to on the road to enlightenment.
Charity - the right arm is shown extended downwards, with the open palm turned to the front and the fingers extended. This 'mudrā is usually associated with a standing Buddha. This position can signify either that the Buddha is granting or receiving alms from his followers.
Absence of fear - either one or both arms are shown bent at the elbow and the wrist, with the palm facing outwards and the fingers pointing upwards. It shows the Buddha either displaying fearlessness in the face of adversity, or encouraging others to do so. The right hand raised is also referred to as "calming animals" and both hands raised are also called "forbidding the relatives". These 'mudrās are usually associated with a standing Buddha, but sitting Buddha variants are also quite common.
Reasoning and exposition - the arm and hand are positioned in the same manner as in the Absence of Fear except that the thumb and forefinger are brought together. The gesture can be made with either the right or left hand but not both. This mudra signifies an appeal to reason. Since the Buddha is appealing to reason, this gesture often represents an appeal for peace.
Setting the wheel in motion - the hands are held in front of the chest, with both hands in the resting position, with the fingers of the left hand resting in the palm of the right hand. This is a less common as it refers to a particular episode in the Buddha's life - his first sermon, when he set the wheel of his life's work in motion. It is used for both seated and standing representations.
Over the centuries combinations and variations of these six different appearances have evolved. As artists depicted more specific incidents in the life of the Buddha, new, secondary mudrās were created, such as "The Buddha holding an alms bowl" and “The Buddha receiving a mango" and the Buddha performing various miracles.