Offering prayers of supplication is primarily a recognition that we need God for everything.
The verb “to supplicate” comes from a Latin word that means “to implore” and has the added prefix of “sub” meaning “from below.” Whenever someone “supplicates,” it is an activity that is done when a person puts themselves lower than someone else.
It makes sense, then, that supplication has become associated with Christian prayer, recognizing that God is far beyond us and we are in need of his help.
The Catechism of the Catholic Church expands on this definition and connects it to other synonyms that helps us understand it.
The vocabulary of supplication in the New Testament is rich in shades of meaning: ask, beseech, plead, invoke, entreat, cry out, even “struggle in prayer.” Its most usual form, because the most spontaneous, is petition: by prayer of petition we express awareness of our relationship with God. We are creatures who are not our own beginning, not the masters of adversity, not our own last end. We are sinners who as Christians know that we have turned away from our Father. Our petition is already a turning back to him. (CCC 2629)
A prayer of supplication, then, is a prayer of petition that asks our Heavenly Father for a particular spiritual or material benefit. It recognizes God’s supreme power over all creation and his ability to grant us what we need.
Prayers of supplication are scattered everywhere throughout the Bible, with the Psalms being the most prime example. If we need any inspiration as to how our prayers of supplication should look like, open up the Psalms and start reading.
When we pray, let us remember that God is God and we are not. He is in control and has a planned marked out for us. It is up to us to turn towards him and away from our sins, asking him to have mercy on our souls.