A group of numbers, symbols and operators is known as an expression. This is an example of an expression: 16x^5 + 45/x^2 + Z Log (x) - 2450. As you can see there you have simbols, numbers and operator. A value is just a number a term is a part of an expression , for example the expresssion used as example has 4 terms (16x^5 is one term, 45/x^2 is other terms, Z log(x) is other term and - 2450 is other therm. An array is a set of elements ordered by rows and columns.