Final answer:
The age group being described in terms of developmental milestones is Toddlers (1-2 years). During this stage, they learn to walk, develop motor skills, and language abilities. Preschoolers (3-5 years) have distinct and more advanced developmental milestones.
Step-by-step explanation:
Child Developmental Milestones
The age group described, based on the referenced material, is Toddlers (1-2 years). During this stage, children learn to walk and bear the title 'toddler' because of their toddling movements. They are in a significant period of developmental milestones including rapid growth in size, although at a slower pace compared to infancy. Their motor skills are advancing, enabling them to walk with help, and they are also acquiring language skills, learning new words, and beginning to form simple sentences.
Preschoolers (3-5 years), on the other hand, have already passed the toddler stage and exhibit different milestones. These children experience an increase in both cognitive and psychosocial development. They start to engage in more complex play, build their vocabulary, and improve their motor skills to include activities like running and climbing with greater coordination.