What is a random variable

In mathematics we learn about discrete and continuous random variable. What is a random variable?

Based on my understanding of the term, I think it means "a quantity that changes in a random, unpredictable fashion."

Please give me a non-technical answer (meaning without using much mathematical terms that I may not understand). Thanks!

When you estimate how long you will stand in line at a restaurant to get your food, you never know how long you will really have to wait. You do not know how many people are in line and you do not know what they are ordering. Those are random variables that affect the time. Every time you go into the restaurant these variables are ALWAYS different and you cannot predict what it will be from day to day.
The variables you cannot predict are the random variables.

I think it would be safe (please correct me if I am wrong, anyone) to interpret a random variable as: "a variable that can take on a number from a of restricted set of values corresponding to a particular event."

For random variables, X

Discrete:

X = heads or tails for coin tosses, but nothing else
X = {1, 2, 3, 4, 5, 6}, for any roll of a die

or

Continuous:

X = percentage on a test score from 0 to 100, the range of X is any real number on that interval

and so on.

It represents a value that a variable can take on in any ol' "random" situation where the if you pick on value of X from a corresponding event, it is "random" in the social use of the word, but of course not truly random since nothing is.