The majority of the day of Yom Kippur is spent in prayer. Indeed it is the only day of the year that we pray five separate prayers.
But what is the essence of prayer?
The Hebrew word for prayer is Tefila, which according to our sages means to create a bond. When we stand before G-d and ask Him to provide for our needs, we thereby enter a relationship with Him. Whether our prayers are supplications or expressions of gratitude, they constitute communication, and when we communicate we are creating a relationship with Him. This relationship is the most precious thing a human being can have.
We find in the very beginning of the Torah that the serpent who instigated Adam to sin was cursed with “you shall eat earth all the days of your life”. Now we have to ask ourselves, what kind of curse is that? The serpent will always have an abundance of food and this hardly appears to be a curse! The answer is quite profound, that the serpent was so despised he was given an inexhaustible supply of food. He will never be lacking, and so he will never need to turn to his Creator. Adam on the other hand was told that he must work for his food and if he will be lacking, he will pray to G-d to provide for him.
The curse of the serpent was that he was totally rejected from entering into any communication or relationship with G-d. The gift of prayer indicates that we are in a relationship with Him, and prayer is the bond and Yom Kippur is the most auspicious time.