I'm afraid I have to disagree. The problem I have with most of the responses is that "Risk" is being defined as an event similar to an issue. The Risk is the impact of an issue/event occuring. For instance, there are many things that can go wrong on a project that will impact the schedule. Plugs aren't right, and you have to order new ones; A PO is sitting waiting for an approval; Your resource was overcome by the Bubonic Plague and had to be quarantined. These are all issues, but the associated Risk is Delay to the Project. The risk of not fixing these issues is that the project will suffer from delays, and the project will not be done in the time expected, or planned. The mitigation plan to avoid these risks is to expedite shipping once a PO is cut; Move equipment to where there are proper outlets, or again, expedite shipping of the plugs; or hire a backup resource; OR modify the end date of your project (if schedule is not the primary concern).
I like to categorize risk by the 4 main ingredients of project management: Cost, Schedule, Scope, and Quality. A cost risk involves the various events that could occur that might send the budget the way of the DoDo. A schedule risk are those described above, those that will positively or negatively impact the schedule. (Yes, there are positive risks too! You just might finish early if your resource is miraculously healed by a traveling witch doctor!) Likewise, a Scope risk is if the requirements are vague, and there is a great chance that new requirements will creep up during execution of the project plan. And of course if your project is under extreme pressure to be completed on time, no matter what, there is a great risk that the quality of the product will suffer as a result, with more attention being focused on getting it done quickly rather than getting it done right.