The definition I’ve heard the most is: newborn (0-3 mo.), infant (3-12ish mo, toddler (from the time they start walking to between about 2-3 years). Technically, any of them could be considered a baby.
“Toddler” describes the action of toddling, or walking in an uncoordinated way.
You’ll love this then: https://www.atlasobscura.com/articles/tourists-love-to-rub-the-bronze-balls-of-wall-streets-charging-bull-statue-why