📝 clarified difference between serialization and string value retrieval

#853

README.md

@@ -207,6 +207,29 @@ std::cout << j.dump(4) << std::endl;
 // }
 ```
 
+Note the difference between serialization and assignment:
+
+```cpp
+// store a string in a JSON value
+json j_string = "this is a string";
+
+// retrieve the string value (implicit JSON to std::string conversion)
+std::string cpp_string = j_string;
+// retrieve the string value (explicit JSON to std::string conversion)
+auto cpp_string2 = j_string.get<std::string>();
+
+// retrieve the serialized value (explicit JSON serialization)
+std::string serialized_string = j_string.dump();
+
+// output of original string
+std::cout << cpp_string << " == " << cpp_string2 << " == " << j_string.get<std::string>() << '\n';
+// output of serialized value
+std::cout << j_string << " == " << serialized_string << std::endl;
+```
+
+`.dump()` always returns the serialized value, and `.get<std::string>()` returns the originally stored string value.
+
+
 #### To/from streams (e.g. files, string streams)
 
 You can also use streams to serialize and deserialize: