What Is Event. Target. Value in React Exactly? [Duplicate]

I was able to implement an event handler in my simple React app and I wanted to understand event.target.value more deeply. I have a guess, but I wanted to ask others so I can confirm or modify any false understandings.

So... how are we able to even use event.target.value in React? Does event belong to the Event Web API that I found here? Or is it more of a React thing?

Here is my code for reference

import React from 'react';
import Display from './Display';

export default class Search extends React.Component{
  constructor(props){
    super(props);
    this.state = { userInput: '' };
    this.onSubmit = this.onSubmit.bind(this);
    this.updateInput = this.updateInput.bind(this);
  }

  updateInput(e){
    this.setState({userInput: e.target.value});
  }

  onSubmit(){
    const title = this.state.userInput;
    console.log(title)
  }
  
  render(){
    return(
      <div>
      <label>
        Movie Search App
        <br></br>
        <input type="text" value={this.state.userInput} onChange={this.updateInput}/>
      </label>
      <br></br>
        <input type="submit" value="Search" onClick={this.onSubmit}/>
        <Display />
    </div>
    )
  }
}