Or 3 Psychology concepts or theories that stood out to me in class

This is my last essay due for PSY 101.
Here is the exact essay that I need to write about:

What Theories and Concepts of Psychology stood out to me? Consider this question when writing your final essay (synthesis paper). Pull together two or three of the theories and/or concepts you learned in this class and expand on them using references like your book or other sources (except Wikipedia).

Theories that have stood out to me are Freuds Psychosexual Theory of Personality and Kohlbergs Theory of Moral Development, but if you know of other theories that are easier to write about, thats fine with me. Thanks:O)