A stochastic process is a collection of randomvariables that is often used to represent the evolution of some random value over time.
In probability theory, a stochastic process--sometimes called a random process-- is a collection of randomvariables that is often used to represent the evolution of some random value, or system, over time.
In the simple case of discrete time, a stochastic process amounts to a sequence of randomvariables known as a time series--for example, a Markov chain.
Randomvariables are non-deterministic (single) quantities which have certain probability distributions.
Randomvariables corresponding to various times (or points, in the case of random fields) may be completely different.