What are the differences between userAge and input in Use a Ternary Expression for Conditional Rendering

[abdulrahman.mhd.anas]

Tell us what’s happening:
I pass the challenge but I have a question.
I pass the challenge when I use this.state.userAge but the challenge was not passing when I used this.state.input
So What are the differences between them ?

const inputStyle = {
width: 235,
margin: 5
};

class CheckUserAge extends React.Component {
constructor(props) {
  super(props);
  // Change code below this line
  this.state = {
    input: "",
    userAge: ""
  };
  // Change code above this line
  this.submit = this.submit.bind(this);
  this.handleChange = this.handleChange.bind(this);
}
handleChange(e) {
  this.setState({
    input: e.target.value,
    userAge: ""
  });
}
submit() {
  this.setState((state) => ({
    userAge: state.input
  }));
}
render() {
  const buttonOne = <button onClick={this.submit}>Submit</button>;
  const buttonTwo = <button>You May Enter</button>;
  const buttonThree = <button>You Shall Not Pass</button>;
  return (
    <div>
      <h3>Enter Your Age to Continue</h3>
      <input
        style={inputStyle}
        type="number"
        value={this.state.input}
        onChange={this.handleChange}
      />
      <br />
      {/* Change code below this line */}
      {this.state.userAge === ""
        ? buttonOne
        : this.state.userAge < 18
        ? buttonThree
        : buttonTwo}
      {/* Change code above this line */}
    </div>
  );
}
}

  **Your browser information:**

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:90.0) Gecko/20100101 Firefox/90.0

Challenge: Use a Ternary Expression for Conditional Rendering

Link to the challenge:

freeCodeCamp.org