Functions are part of the foundation of JavaScript. Functions help define specific tasks or calculations of a value. Functions generally read more like an equation as they are setting limits to find an end result. A function only accesses the variables located within it’s global space. This means if a function is inside of a function it can only access it’s own variables and not the parent function’s variables.
These are strings of code that resolves a value. Expressions include primary expressions, string, and logical expressions.