"The boy has a cake."
Translation:Cậu bé có một cái bánh.
"Chú bé" means a young male, i. e., a little boy.
Alternatives are: "thằng bé", "thằng nhỏ", "cậu bé".
Note: In a family context, "chú" means your paternal uncle, who is younger than your father. "Bác" is the older one, for those who are curious!
By extension, "chú" can also be used to address a man you meet in the street.
The above is just a quick glimpse into the complexity of the topic but you'll pick it up as you progress.