Clarification on references

src/basic-syntax/references.md

@@ -11,9 +11,18 @@ fn main() {
 }
 ```
 
-Some differences from C++:
+Some notes:
 
-* We must dereference `ref_x` when assigning to it, similar to C pointers,
+* We must dereference `ref_x` when assigning to it, similar to C and C++ pointers.
 * Rust will auto-dereference in some cases, in particular when invoking
-  methods (try `count_ones`).
+  methods (try `ref_x.count_ones()`).
 * References that are declared as `mut` can be bound to different values over their lifetime.
+
+<details>
+Key points:
+
+* Be sure to note the difference between `let mut ref_x: &i32` and `let ref_x:
+  &mut i32`. The first one represents a mutable reference which can be bound to
+  different values, while the second represents a reference to a mutable value.
+
+</details>