In John 3:16, Jesus states that whoever believes in him will have eternal life. The word that gets translated as believe is the Greek word pisteuō. It is used in John about 100 times, the most out of any book in Scripture.
Belief in Jesus is the only requirement he gave us in order to be saved. Yes, he taught many things, and told us how to live. But, the only condition for salvation is to believe in him.
The definition of believe as it is used in 3:16 is, “to believe to the extent of complete trust and reliance.”
Another way to define believe is, “to embrace something as true,” and when it’s a person, it means, “you trust them to be and do what they have claimed.”
In the case of Jesus, he is claiming to be the Son of God and the source of eternal life. He claims to be the means to salvation from sin.
If we were to include this definition in the verse, here is how it would read: For God so loved the world that he gave his only Son, that whoever puts their complete trust and reliance on him for salvation will not perish but have eternal life.
In English, believing does not necessarily imply trust. So, I must ask, do you merely believe Jesus, or do you trust him? If you trust him, you will need to get to know him and start behaving as though you trust him to be who he says he is.