To make this poem a little more fun, let's imagine it from the lamb's perspective. There we are, munching on some grass in a beautiful English valley, when suddenly some little rug-rat kid comes running up for a chat. He asks if we know who made us, to which our answer is, "(Munch, munch) This grass is delicious!"
He asks if we know who gave us life and made us eat this sweet, sweet grass as we roam through fields and next to streams. He asks if we know who gave us our "clothing wooly bright" (6) and our pleasant voices.
Then he says he's going to tell us who made him. He says our creator is also called a "Lamb" because he was so "meek" and "mild" (15). Despite being a lamb, this creator also "became a little child" (16).
Finally, he blesses us twice in the name of God and runs away.