CBT is based on the concept that your thoughts, feelings, physical sensations, and actions are interconnected and that negative thoughts and feelings can trap you in a vicious cycle. CBT aims to help you deal with overwhelming problems in a more positive way by breaking them down into smaller parts. You're taught how to change these negative patterns to improve the way you feel.
Unlike some other talking treatments, CBT deals with your current problems, rather than focusing on issues from your past. It looks for practical ways to improve your state of mind on a daily basis.