autocomplete attribute allows automated assistance in filling out the form field values.

Sample Lightning Web Component:

HTML:

<template>
    <div class="slds-box slds-theme--default">
        <form>
            <lightning-input
                label="First Name"
                type="text"
                autocomplete="given-name"
                name="firstName">
            </lightning-input>
            <lightning-input
                label="Last Name"
                type="text"
                autocomplete="family-name"
                name="lastName">
            </lightning-input>
            <lightning-input
                label="Company"
                type="text"
                autocomplete="organization"
                name="company">
            </lightning-input>
            <lightning-input
                label="Email"
                type="email"
                autocomplete="off"
                name="email">
            </lightning-input>
            <br/>
            <lightning-button
                label="Submit"
                type="submit">            
            </lightning-button>
            <lightning-button
                label="Reset"
                type="reset">            
            </lightning-button>
        </form>
    </div>
</template>

JavaScript:

import { LightningElement } from 'lwc';

export default class SampleLightningWebComponent extends LightningElement {}

js-meta.xml:

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>60.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__Tab</target>
    </targets>
</LightningComponentBundle>

Output: