What does ${} (dollar sign and curly braces) mean in a string in Javascript?

You can also perform Implicit Type Conversions with template literals. Example:

let fruits = ["mango","orange","pineapple","papaya"];

console.log(`My favourite fruits are ${fruits}`);
// My favourite fruits are mango,orange,pineapple,papaya

As mentioned in a comment above, you can have expressions within the template strings/literals. Example:

const one = 1;
const two = 2;
const result = `One add two is ${one + two}`;
console.log(result); // output: One add two is 3

You're talking about template literals.

They allow for both multiline strings and string interpolation.

Multiline strings:

console.log(`foo
bar`);
// foo
// bar

String interpolation:

var foo = 'bar';
console.log(`Let's meet at the ${foo}`);
// Let's meet at the bar