Career planning is, in general, a continuous process in which an individual evaluates what he/she wants to do, what one needs to do to achieve those goals, etc. Whether one is in school or college or mid-career level, everyone does some form of career planning (some maybe more extensive than others). We often hear children say that they want to be a doctor or an engineer or a teacher and many of them do enroll in medical or engineering or teaching programs and college and end up in the profession of their choice. That is, they decided on what they like or want to do, took actions to support that decision and achieved it. Career planning does not stop at just getting a job of choice, it continues throughout one's career. For example, someone is an engineer today, but can be a project director or manager in the next 10 years or partner in 20 years or open his/her own company in the next 2 years, etc. Career planning includes figuring out what one wants or likes, finding out the possibilities, making some decisions (from among the choices) and taking action to follow through with the chosen decision.
Hope this helps.