What does John means when he says that God is Love? What love he is talking about? I s it the same if we say that Love is God?
What John means is that, biblically, love is defined by God’s relationship with us. This is love, not that we loved him, but that he loved us, and gave his Son as an atoning sacrifice for our sins.” There are many ways to define the word love. There is love of husband for wife, of parent for child, of friend for friend, of human for pet, of human for pizza, of person for nature and so forth. John is not trying to dismiss these “dictionary) definitions. What he is saying is that the essential nature of that deep human-felt need–the need for love–is filled by God. There is no example to explain love better than God’s feeling for us. God is not just loving. God defines love. It is impossible for God to do anything which is not controlled by his love. God never does an unloving act. Ephesians 3:18 helps to explain why we can say that “God is love.” “I pray that you, being rooted and established in love, may have power, together will all the saints, to grasp how wide and long and high and deep is the love of Christ, and to know this love that surpasses knowledge–that you may be filled to the measure of all the fullness of Christ.”
In all these senses, “God is love.”
On your second question, no, we cannot say that “love is God.” The reason is that God is more than just love. He is power, he is Creator, he is justice, he is wisdom, he is Savior. God defines love, but love does not define God.