Psychology explores the immediate causes of our actions rather than the final causes of our action. This is called "determinism". Psychologist James Kalat describes determinism as, "the assumption that everything that happens has a cause, or determinant, in the observable world." Psychology works to find if the same is true for human behavior--if everything we do has a cause. Humans possess free will, "the belief that behavior is caused by a person's independent decisions."
Psychologists are trying to solve the mind-brain problem. The mind-brain problem asks the question: What is our mind? By taking a psychology class, you can form your own opinion. Our bodies are run by the physics and chemistry of the nervous system. We live in a world full of matter and energy, so psychology is trying to find why we have a conscious mind at all. There is one theory, "dualism," which states: "the mind is separate from the brain but somehow controls the brain and therefore the rest of the body." This theory was first put forth in the 1600s and is still debated today.
You have probably heard the argument "nature vs. nurture" used when someone is trying to justify the bad behavior of an individual or why one child may be intelligent and why another struggles in school. This section of psychology tries to find whether our behaviors and choices our influenced by our genetics or by our environmental factors. Psychologists also study the issue of gender differences between boys or girls to see if male and female behaviors are inherent or enforced. Studying psychology will help you gain more information on the issue so you can form your own conclusions.
You may be interested in one field of psychology but not another. That is fine, as psychologists study a wide variety of subjects. These subjects include biological psychology, which tries to explain our behavior based on biological factors; evolutionary psychology, which tries to explain our behavior based on the evolutionary history of our species; learning and motivation, which studies how our behavior depends on past outcomes and current motivations; cognitive psychology, which studies how we think and acquire knowledge; developmental psychology, which studies our behavioral capacities at different stages of life; and social psychology, which studies how other people influence an individual. There are many subbranches of each individual field of study and new fields are being formed every day.