Baby: a very young child, especially one newly or recently born.
A baby has different stages. There’s newborns which usually refers to a baby from birth to about 2 months of age.
Also, infants can be considered children anywhere from birth to 1 year old.
Baby is a term that can be used to refer to any child from birth to age 4 years old, thus encompassing newborns, infants, and toddlers.