The formal term for using ${} syntax in template literals is 'expression embedding' or more commonly 'template interpolation.' This feature allows you to embed any valid JavaScript expression within a string using the ${expression} syntax. The expression is evaluated, and its result is converted to a string and inserted into the final string value. Template interpolation is more powerful than simple variable substitution because you can include not just variables but any valid JavaScript expression—function calls, arithmetic operations, ternary operators, and even other template literals. This enables more dynamic and concise string construction compared to traditional concatenation methods.