Rishis have selected the words of various Mantras and arranged them in such a way that they not only convey some meaning but their chanting also creates specific energies. Gayatri is a mantra which inspires righteous wisdom. It means that the Almighty God may illuminate our intellect, which may lead us on the righteous path. This is the most important prayer.

Om Bhurbhuvah Swah
Tatsaviturvarenyam
Bhargo Devasya Dhimahi
Dhiyo Yo Nah Prachodayat ॥

Om! - Brahma or Almighty God
Bhuh - Embodiment of Vital Spiritual Energy (Pran)
Bhuvah - Destroyer of Sufferings
Swah - Embodiment of Happiness
Tat - That
Savituh - Bright, Luminous like the Sun
Varenyam - Best, Most Exalted
Bhargo - Destroyer of Sins
Devasya - Divine
Dhimahi - May Imbibe
Dhiyo - Intellect
Yo - Who
Nah - Our
Prachodayat - May Inspire

(Source: http://www.awgp.org)