So, what is Psychology and what will I study?

The word Psychology comes from Two words: Psyche and logos. The word psyche is from a Greek word meaning "breath of life", i.e. "soul or spirit", loosely translated as MIND. The word logos means "knowledge' or "study".
Therefore, the word Psychology can be roughly translated as the study of the mind. There are literally hundreds of definitions of Psychology, however, a generally accepted term is "the scientific study of the mind and behaviour".