Child development refers to how a child is able to do more complex things as they get older. Development is different than growth. Growth only refers to the child getting bigger in size, whereas development is overall growth of the child. Here, the growth is not restricted to size but intellect as well. When we talk about normal development, we are talking about developing skills like:

Gross motor: using large groups of muscles to sit, stand, walk, run, etc., keeping balance and changing positions.
Fine motor: using hands to be able to eat, draw, dress, play, write and do many other things.
Language: speaking, using body language and gestures, communicating and understanding what others say.
Cognitive: Thinking skills: including learning, understanding, problem-solving, reasoning and remembering.
Social: interacting with others, having relationships with family, friends and teachers, cooperating and responding to the feelings of others.