Quite a confusing term if you are not a programmer. String interpolation is a programming language feature that helps coders generate words dynamically. Let's say I have an app that displays Hi Emem. You can bet the programmer used string interpolation to generate the "Emem" part of  "Hi Emem".

But string interpolation is not the only way to generate human readable messages, we have always had string concatenation.  So why string interpolation what difference does it make? A comparison will help

The above is an example of string concatenation in javascript, notice we had to use + operator to combine the two strings (words) not very natural right? Exactly. Now let's see an example of string interpolation

So whats the difference? Placeholders! The ${your_variable_name_here } syntax allows you to format the sentence or phrase as you please, inserting placeholders wherever you need dynamic content.

Let's say you are developing an appointment reminder system. The system needs to generate email reminders to your clients about their upcoming appointment. The wording of the email may go like this:

Dear ${name},  

You have an appointment with us on the ${date_of_appointment} at ${time_of_appointment}.

We look forward to seeing you

Your programming language will understand that it needs to replace  ${name} with the actual name of the client, ${date_of_appointment} with the appointment date and ${time of appointment} with the appointment time. Here follows an example

If you have node installed, you can copy, paste and run that example at the node prompt. I hope you can see why we love string interpolation - it makes it so easy to generate message templates.