God's nature is described in three ways by John. It is by no means a complete description, but it helps understand God's nature. God's love is holy love. Much of what is called love in society bears no resemblance to holy love. Some even try to dignify immorality by calling it love.
Christian love is a special kind of love.
There is a false love, and that's the love God rejects. Christian love is given from God. To know God is to be in a deep relationship with Him. It's to share His life and enjoy His love. Knowing this isn't simply understanding the facts, it's a matter of understanding the truth.