If we look at the Wikipedia definition of a variable:
In computer programming, a variable is a storage address (identified by a memory address) paired with an associated symbolic name, which contains some known or unknown quantity of information referred to as a value
And for expression, we get the following definition:
An expression in a programming language is a combination of one or more constants, variables, operators, and functions that the programming language interprets and computes to produce another value.
That said, let's see how to use variables and expressions in your Infinable applications to handle dynamic data.