Regex help Quality Assurance and Testing

[nsgxyz]

    test('#match, #notMatch', function () {
      const regex = /^#\sname\:\s[\w\s]+,\sage\:\s\d+\s?$/;
      assert.notMatch(formatPeople('John Doe', 35), regex);
      assert.notMatch(formatPeople('Paul Smith III', 'twenty-four'), regex);
    });
  });

I can not find a reference for what the # character does in the Regex for this example.

Can you point me in the direction that documents this?

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Challenge: Use Regular Expressions to Test a String

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[nsgxyz]

never mind. I see that it is coming from the

 const formatPeople = function (name, age) {
    return '# name: ' + name + ', age: ' + age + '\n';
  };

function.