apiDecoratorExample.html

<template>
  <div>
    <button onclick={toggleVisibility}>Toggle</button>
    <template if:true={isVisible}>
      <div>This element is visible</div>
    </template>
  </div>
</template>

<script>
import { LightningElement, track } from 'lwc';

export default class VisibilityToggle extends LightningElement {
    @track isVisible = false;

    toggleVisibility() {
        this.isVisible = !this.isVisible;
    }
}
</script>