This is possibly the first memory verse I learned as a child. It says a lot. First, it says that God loves us. Second, it says that God loves us. Third, it says that God really does loves people.
Yet, there are obvious thoughts in just this one passage that also teaches that people need to love Him. First, people must believe in God. Second, people must believe in who Jesus is as God's Son. Third, people must believe.
Like all passages in the Bible (as well as any other good literature) context of what one is reading is important. What does begotten mean? What does belief mean? How can a person perish? What is eternal life?
Within the context of a particular passage things can be answered. Within the context of the letter, it is written in, meaning can be understood. When one looks at the entirety of Scripture - well, duh - understanding leaps from the pages to your heart and mind.
Now, look at this "He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him" (John 3:36). Is there understanding within this context. Belief means understanding who Jesus is as God's Son and being obedient to His teachings. It is not enough to say the words "Jesus is God's Son" as if your making some sort of incantation. Belief entails action.
Perishing is the idea of not having eternal life; rather, eternal death (God's wrath). So, to have eternal life not only necessitates understanding who Jesus is but also following His teachings that come through the word (cf. John 17:20-21).
Be the Lord's humbled and let Him guide you through His word.
The Lord's humbled . . . John A. Reeves