B'tzelem elohim. "Image, Likeness, Outline, Shadow"
It means we have the ability to think into the future, and to envision and plan and create.
I don't think it is because we LOOK like God, rather because we can act like God. We can be kind and merciful, and noble and self-sacrificing. We can be forgiving when we don't have to be, we can be altruistic.
I do not deny the possibility that dolphins and apes and other animals can also be some of these things. It is not necessary for us to be exclusively like God. We can be like God inclusively -- ALONG with dolphins and apes. That others feel love for their young does not somehow diminish me or make me less human.
Tselem (Hebrew) A form, image, likeness; a shadowy image, a shadow. Hence also the astral "shadow" of the human physical body -- the model-body or linga-sarira. It corresponds to the Sanskrit chhayas: in the tselem of 'elohim was made 'Adam (Zohar iii, 76, Crem ed.), i.e., in the image of the pitris was fashioned mankind (cf Genesis 1:27); but not only "in the image" but likewise of the substance of the shadow itself humanity was formed; in other words, the pitris projected their astral shadows which became the lower principles of the individuals of the human race.