Child
A child is a young boy or girl in the care of parents, older than a suckling or an infant, but not yet an adolescent. "Children" are sometimes used as a name for a large group of descendants of one person, such as the Children of Israel, or even all human beings as the Children of Men. A child represents innocence and charity, where innocence is the willingness to be led, and charity is love. This is why Jesus blessed them and suggested that we all become like children in order to enter heaven.
Isaiah 65:17-19
17
"For, behold, I create new heavens and a new earth; and the former things shall not be remembered, nor come into mind.
18
But be you glad and rejoice forever in that which I create; for, behold, I create Jerusalem a rejoicing, and her people a joy.
19
I will rejoice in Jerusalem, and joy in my people; and there shall be heard in her no more the voice of weeping and the voice of crying.