Need of this.functionName

why do I need to use this.functionName
can’t I simply use function name ?

class Counter extends React.Component {
 constructor(props) {
   this.state = {
     count: 0
   // change code below this line
this.increment = this.increment.bind(this);
   // change code above this line
 // change code below this line

 // change code above this line
 render() {
   return (
       <button className='inc' onClick={this.increment}>Increment!</button>
       <button className='dec' onClick={this.decrement}>Decrement!</button>
       <button className='reset' onClick={this.reset}>Reset</button>
       <h1>Current Count: {this.state.count}</h1>

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Challenge: Write a Simple Counter

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I guess “this” refers to the instance of the object you created. You can use function name directly but this keyword helps to create multiple instance of an object. Like, you’re using multiple buttons here. Code reusability is what functions are good for.