Terminology

Term	Definition
LINQ	Stands for `L`anguage `IN`tegrated `Q`uery. It is a set of methods our various collections (e.g. `List`) will acquire once we add `LINQ` to our codebase.
Expressions	A combination of operands (variables, literals, method calls) and operators that can be evaluated to a single value.
Select	Makes a new list, of `equal size`, by running an expression on every item in the list and using that value when filling the new list.
Count	Determines and returns how many items are in our list.
Where	The `Where` statement is like a filter. Makes a new list, of equal or smaller size by running an expression against every item, keeping items when the expression returns `true`.
Aggregate	Returns a single value. It starts with a value we will call the `current value`. The given expression gets to use, one at a time, the current value and the item from the list, returning a new `current value`
Sum	Returns an integer by adding up the value of the expression for each item.
All	Returns a boolean if the expression evaluates to `true` for every element in the list.