Choking occurs when the airway is blocked with something that prevents the intake of oxygen.
Hot dogs are a common food that can be dangerous as well as hard candy. Ever wonder why Life Savers candy has a hole in the middle? The hole was added to save people from choking. Hot dogs should be cut into very small pieces before given to toddlers and they need to be supervised while eating them.
You could indeed choke on anything, but one small popcorn hull isn't gonna do it. It could go down your windpipe and cause you to violently cough to dislodge it though.
It is important to chew your food well before you swallow, no matter what you are eating.