Wikipedia (http://en.wikipedia.org/wiki/God_the_Father) tries to define who God the Father is. He is the God-Creator of Judaism and of Christianity.
To Christians, God the Father's relationship with humanity is as a father to children. Thus, humans in general are sometimes called children of God. To Christians, God the Father's relationship with humanity is that of Creator and created beings, and in that respect he is the "Father" or "Life-giver" of all. The New Testament says, in this sense, that the very idea of family, wherever it appears, derives its name from God the Father,[Eph 3:15] and thus God himself is the model of the family.
However, there is a deeper sense in which Christians believe that they are made participants in the eternal relationship of Father and Son, through Jesus Christ. Christians call themselves adopted children of God:
“ But when the fullness of the time had come, God sent forth His Son, born of a woman, born under the law, to redeem those who were under the law, that we might receive the adoption as sons. And because you are sons, God has sent forth the Spirit of His Son into your hearts crying out, "Abba, Father!" Therefore you are no longer a slave but a son, and if a son, then an heir of God through Christ.(Galatians 4:4-7) ”
God the Father is Agape personified - as He gave to us His only Son to redeem us, and adopted us as His children.
What better way is there to describe a real father. One who loves us eternally with a depth unimaginable to the human mind. He gave us a free will that He honors even if it means that we abandon Him. What greater love can a father have for His children that He offered His begotten Son, Jesus Christ, to carry our sins and suffer for our sins. Always seeking out for our own good.....
And yet in our age and time, we forget Him - even as He continually nurture our very existence every moment of our lives.
To a majority of mankind, He is still just a theory, and ideology, a concept. Yet He is as real as His creations.
It is sad that after all that He has done and is doing, we fail even in the smallest measure, to see the reality of His existence.
God the Father asks that we love Him as a response to His love for us. Jesus Christ has told us about the love of God the Father for us. He thirst for our love for Him.
On Father's Day - let us give Him thanks and praise. He is the best Father we can ever have.