Project Risk Definition
There may be external circumstances or events that cannot occur for the project to be successful. If you believe such an event is likely to happen, then it would be a risk. Identifying something as a risk increases its visibility, and allows a proactive risk management plan to be put into place.
If an event is within control of the project team, such as having testing complete by a certain date, then it is not a risk. If an event has 100 percent chance of occurring, then it is not a risk, since there is no "likelihood" or risk involved (it is just a fact).
Examples of risks might be a"Reorganization may result in key people being reassigned," or "The new hardware may not be able handle the expected sales volume."
I've also put together a short online course that describes project management fundamentals if you're interested in learning more about this profession.