What are /* */ characters in the solution code of mission: Exploring Tables, screen: 3?

Screen Link: https://app.dataquest.io/m/576/exploring-tables/3/the-order-of-clauses

The above screen’s solution code is surrounded by /* */ characters. But this is not taught in any of the previous missions or screens.

/* */ characters are used to create block comments. You can read more about this on screen 3 of the Coding with Style mission.

The SQL engine ignores block comments, so it can be used to either create a short description about your query so that it’s easier to understand, or it can be used to prevent a part of the query from being executed by the SQL engine for debugging purposes. In this case, we used it to prevent our system from running the illegal query:

SELECT *
 LIMIT 5
  FROM invoice_line;

If we allow this to run, it will result in an error and create issues with the mission. So, in short, it is done to ensure that the mission works correctly on your end. You can safely ignore that.