As a tool, Content Banks is not linked to any module, i.e. it is not displayed on the left navigation bar of your module. Instead, you can find it on the top blue bar.
Content Banks is meant for you to store questions and rubrics, so that these can be re-used in different assessments or across modules. When you enter Content Banks, you will see the Questions and Rubrics options on the left hand side.
Questions banks can be used to store questions that you can use in Quiz, Survey, or Poll. These banks can be shared with other users so that they have access to the questions.
The Rubrics section allows you to create rubrics that you can use in different assessments. It will also automatically store any rubrics that you create through tools such as Quiz or Gradebook.