Monte Carlo Simulations
Monte Carlo methods are a type of simulation where we repeat a trial many times in order to take advantage of the law of large numbers and get estimates of some behavior or measurement.
There are other kinds of simulation as well though that don't rely on multiple trials. For example, you could imagine writing physics equations to model the acceleration/velocity/position of a car, and then using those equations you can run a single simulation to determine, say, the location of the car after some time with a given acceleration and velocity. In this case, you only used a single trial, and since there was no randomness involved in the equations, there's no need to use more than one trial. You just take the output of the simulation.
An excellent overview of how to party with Python. See also: an explanation of the technique by Sukanta Deb.