Add clarity around terms

internal/i18n/README.md

@@ -24,8 +24,38 @@ To update an existing language:
 
 1.  Find the language in the `locales/` folder.
 
+1.  Update the language on line 3.
+
 1.  Update the `msgstr` fields to the new values.
 
 1.  Save the file.
 
 1.  Submit a pull request.
+
+
+## Terms
+
+-   **realm** - public health authority, state, or hospital system. The system
+    is multi-tenant, and a user can be a member of multiple realms. For example,
+    the same doctor might operate clinics across state lines. In the US, each
+    state is a "realm". In other areas, a realm could be a country or region.
+
+-   **case worker** - someone at a health clinic, testing facility, doctor's
+    office, etc that is managing cases related to COVID-19.
+
+-   **patient** - the person who is being given a test result for COVID-19.
+
+-   **short code** - 6-8 digit (numeric-only) code that is
+    dictated to a patient by a case worker over the phone.
+
+-   **long code** - 16+ alpha-numeric code that is sent to the patient via an
+    SMS text message. This requires the patient to provide a phone number. If no
+    phone number is provided, no long code is generated.
+
+-   **backup code** - 6-8 digit (numeric-only) code that is dictated to a
+    patient by a case worker over the phone **if and only if** the long code
+    fails to dispatch (e.g. due to network issues). This requires the patient to
+    provide a phone number. If no phone number is provided, no backup code is
+    generated.
+
+-   **signing key** - this refers to an asymmetric signing key (cryptography).