How to make a career plan

For most of the time, I'm totally confused when it comes to the a career plan. Frankly speaking, I know very little about that so-called plan and not to mention, how to work it out . However, people around me are talking about that it all the time. especially Since I have worked for 3 years, in their opinion, it's really the time I should think about about my own plan. But how? Can you help me for that with this? I will be grateful if anyone can could give me some advice. Thanks!