Hey there, $firstname
Hello, Mrs. Redmond
The main difference from using a single quote vs a double quote is that in a single quote, the variables inside the string are not parsed (meaning that the string is interpreted/printed in the exact same way as it was written or typed. (no variable interpolation). Meanwhile, in a double quote, the variable inside the string is parsed, meaning that the system that you’re on knows how to identify when a variable is being used inside a double quote or not. (has variable interpolation).