What are the different types of infant formulas and their characteristics?

Infant formulas can be classified into two categories: standard and special.
Standard formulas are designed to be as similar as possible to breast milk and are considered an alternative food for infants who do not consume breast milk.
Special formulas are designed for specific situations where the infant has different nutrient requirements than a 'normal' child.
Standard formulas include starter formulas, follow-up formulas, and growth formulas.
Special formulas include those for premature infants, transition formulas, lactose-free formulas, and formulas for infants with metabolic disorders.
Infant formulas should only be used as a substitute for breast milk in infants for whom breastfeeding has been contraindicated for medical reasons.