Exp suffix appended to arguments/variable in Tagged Templates (JavaScript)

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals#Tagged_templates

This is the code from the link above:

    let person = 'Mike';
let age = 28;

function myTag(strings, personExp, ageExp) {
  let str0 = strings[0]; // "That "
  let str1 = strings[1]; // " is a "
  let str2 = strings[2]; // "."

  let ageStr;
  if (ageExp > 99){
    ageStr = 'centenarian';
  } else {
    ageStr = 'youngster';
  }

  // We can even return a string built using a template literal
  return `${str0}${personExp}${str1}${ageStr}${str2}`;
}

let output = myTag`That ${ person } is a ${ age }.`;

console.log(output);
// That Mike is a youngster.

There's no documentation related to the Exp suffix and how it is able to call variables with the correlated prefix. Anyone know where I can learn more or what is happening here?

The Exp suffix isn't special, it's just part of the variable name (it's an abbreviation of expression). From the MDN link you included:

The first argument of a tag function contains an array of string values. The remaining arguments are related to the expressions.

Your template has 3 string chunks separated by expressions (an expression is ${} with something inside of it), and those chunks are "That ", " is a ", and "." So, the first argument, called strings in this case, would be ["That ", " is a ", "."]. There are two expressions, person and age, so they would be put into the subsequent arguments: the second argument would have the value of person, and the third would have to value of age. This is perhaps best illustrated in this snippet:

function myTag(strings, a, b, c) {
    console.log(a, b, c);
}

myTag`foo ${1 + 1} bar ${2 + 2} baz ${3 + 3}` // logs 2 4 6