finished ch7.2 and started ch7.3

Modules and Use.md

@@ -70,3 +70,9 @@ pub struct Asparagus {}
 ```
 
 ## Grouping Related Code in Modules
+used to group code together and make easier to reuse
+modules allow for the control of privacy, implementations needs to be declared as public otherwise it will be private by default not available to other modules if private
+
+public modules and implementations can allow for different code to depend on it
+
+this should be used to organize code like a file directory