A random variable is a variable that assumes numerical values associated with the random outcome of n experiment, where one (and only one) numerical value is assigned to each sample point. It may also be used to quantify unquantifiable processes.
Discrete: A variable whose values take only a finite number of values. The best example of this variable is a dice.
Continous: Unlike discrete variables, continuous random variables can take on an infinite number of possible values.
A sample space is the set of all possible outcomes in a random experiment.
Probability, is the chance of an event occurring.
A probability distribution for a discrete random variable consists of the values that the variable can assume and the probabilities associated with the values.
Discrete probability distributions can be presented by using a graph, table or notation formula.