Psychology is often misunderstood as a subject that will help you know what others are thinking, to read their minds and hypnotise people. That is a big myth.
What is true of the discipline is its ability to explain why people think, feel and behave the way they do. Hence goes the definition, Psychology is the science of mental processes, experiences and behaviours.
I like to remember this as a simple A, B and C.
A for affection or emotion (in psychological terms)
B for behaviour and
C for cognition