dataBinding.html

<template>
  <lightning-card title="one way data binding demo" icon-name="custom:custom1">
    <div class="slds-p-around_medium">
      <h1>My full name is {fullname}</h1>
    </div>
  </lightning-card>

  <lightning-card title="Two way data binding demo" icon-name="custom:custom2">
    <div class="slds-p-around_medium">
      <lightning-input
        type="text"
        name="title"
        label="Enter your title"
        value={title}
        onkeyup={changeHandler}
      >
      </lightning-input>
    </div>
    <div class="slds-p-around_medium">
        <p>My title is {title}</p>
    </div>
  </lightning-card>
</template>

dataBinding.js

import { LightningElement, track } from 'lwc';

export default class DataBinding extends LightningElement {
    
    fullname = "Salesforce troop"
    // @track title ="Salesforce developer"
    title ="Salesforce developer"
    changeHandler(event){
        this.title = event.target.value
    }
}

dataBinding.js-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>48.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>
    </targets>
</LightningComponentBundle>