What is stamina? A simple definition would be having the strength and energy to do something over a long period of time - however, it is a relative concept, depending on what you are talking about.
To give an example, when people talk about track and field events, they describe the 400 metres as being a sprint race that requires stamina - yet it is all over in under a minute!
At the same time, long distance events such as triathlons of marathons are said to be great tests of stamina.
So ultimately it means having the ability to perform a given event to a good level right through to the end.
The question for many people is how do you build stamina? Can you improve it with the right training? The answer is an emphatic yes.
The key is targeted training. Whereas most people simply work on being able to cover the given distance, with the right training you can develop the ability to stay strong right to the end.
Before you can do so you have to lay down a base of endurance and strength through appropriate cardio and gym work. Once you have done so you can work on improving your finishing ability.
The workouts that target this are race-pace workouts. These are advanced workouts, typically performed right at the Aerobic/Anaerobic Threshold (around 85% of Maximum Heart Rate). By working at this pace on a regular basis you train your body to hold a good pace right the way through to the end of a race.