Normal crying in infants is typically intermittent, occurs for various reasons such as hunger, tiredness, or discomfort, and can be soothed with gentle care and attention. On the other hand, colic refers to excessive and intense crying in an otherwise healthy and well-fed baby. Colic episodes often last for hours, occur regularly, and can be accompanied by signs of discomfort like clenched fists, arched back, and difficulty soothing.