The Translations feature allows you to replace the names of menus, tabs, headers, warning messages, text fields, etc. on your interface with the text of your choice.  Most of the time, this involves simply locating the key to translate and typing in the custom translation string, which will replace the default string.

While most of the default translations are plain text strings, you'll notice that some of them contain special values within % and { }. Here is an example.

These are variables inserted into the default string that will dynamically be replaced by the values that it holds internally. In the above example, the %{recipient} interpolation will be replaced by the name of the email recipient in real-time.

It is worth noting that these values work only if they are used as-is because the substitution is accomplished programmatically. 

So if you were to customize the above translation string, you could use 'Dear %{recipient}!', but not 'Dear %{user}!' or 'Dear %{recipient} %{recipient_lastname}!', because 'user' or 'recipient_lastname' is not a keyword that Amplify's code will understand.  Although you might not see any errors if you use incorrect interpolations, it will cause unwanted results.