The Sages ordained that "one should not derive benefit from this world without first reciting a blessing." Making a blessing before eating is tantamount to "asking permission" from G-d, acknowledging that "the world, and everything in it, is G-d's" (Psalms 24:1) and G-d is the true source of all the gifts of life. It imbues the mundane act of eating with a spiritual awareness--awareness of the true Source of our sustenance, and of the purpose of eating.
We make different blessings for different food types before eating, and after-blessings when the repast is complete.
