Age specific questions from about 3 months to about 1 year of age. Younger: newborn. Older: toddler.
This age specific tag covers questions about infants after they realize there's more to the world than eating, sleeping and filling a diaper, but before they start toddling around on 2 feet, so say from about 3 months of age to about 1 year.
A rule of thumb: this timeframe ends roughly when they become seriously mobile.