sql.query is a function that will receive two arrays, one is the strings part, the other is the injected values... the template processor takes those arrays and turns it into a parameterized query to the database.
Backticks by themselves will do string interpolation. But backticks with a function name in front will do something a bit different. In this case 'sql.query' is a function and the JS will pass it an array which represents the contents of the backtick string. There the function can do what it likes and return a result. 'sql.query' builds a proper (and safe!) SQL query and executes it.
The backtick feature in ES2015 is really cool and allows for some great DSL type features.
