feat: improve wording about var

Co-authored-by: Alex Younger <[email protected]>

foundations/javascript_basics/variables_and_operators.md

@@ -110,7 +110,7 @@ So in summary, there are two ways to declare a variable:
 - `let`, which we can re-assign.
 - `const` which we **can't** re-assign and will throw an error if we try.
 
-There is also a third way - using `var`. It's similar to `let`, but it is the old way and should **not** be used. However, you will likely come across code which uses `var`, so it is useful to know that it exists. Do not worry too much about it for now.
+There is also a third way, `var`, which was the original way variables were declared in JavaScript. `var` is similar to `let` in that variables assigned this way can be reassigned, but it has other quirks that were cleared up when the language introduced `let` and `const`. By and large, it is not used anymore. However, you will likely come across code which uses `var` at some point, so it is useful to know that it exists.
 
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