Physically, threes generally have a lot of energy and they are very active. Most three-year-olds can ride a tricycle, climb, run, and throw a ball. As they get closer to three and a half, many children can hop on one foot for a short period of time and walk up or down steps using alternating feet. Three-year-olds are capable of feeding themselves with a fork and spoon and putting on their own clothes (although they will need help with buttons, buckles and laces). Most children become toilet-trained during their three-year-old year, although some boys take longer to develop this skill.
In terms of intellectual development, three-year-olds are extremely curious and spend much of their time watching, ...
This answer lists typical developmental characteristics of three-year-old children. I give examples of characteristics in the areas of cognitive (intellectual) development, physical development, social development and emotional development.