Getter Setter Method in LWC.

1. Create a LWC component named as "getterSetterExample". Where getterSetterExample.js has a getter and a setter method for "greetingMessage" and in "getterSetterExample.html" we will call "greetingMessage" message
to display.

getterSetterExample.html

<template>
    {greetingMessage}
</template>

getterSetterExample.js

import { LightningElement, api } from 'lwc';

export default class GetterSetterExample extends LightningElement {
    
    //Get method use to return greeting message.
    @api
    get greetingMessage(){
        return this._greetingMessage;
    }

    //Set method use to setup greeting message in upper case.
    set greetingMessage(value){
        this._greetingMessage = value.toUpperCase();
    }
}

2. Now call this "getterSetterExample" component from "useGetterSetter" component.

useGetterSetter.html

<template>
    <lightning-card title="Getter Setter Example">
        <lightning-layout>
            <lightning-layout-item>
                <!-- Passing greeting-message in small letter and expected result: message will be shown in capital letter. -->
                <c-getter-setter-example greeting-message="hello everyone. welcome to lwc getter setter example."></c-getter-setter-example>
            </lightning-layout-item>
        </lightning-layout>
    </lightning-card>
</template>

Now to make this useGetterSetter available in AppBuilder/Record Page/Home Page, please update "useGetterSetter.js-meta.xml" file as below,

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata" fqn="useGetterSetter">
    <apiVersion>45.0</apiVersion>
    <isExposed>true</isExposed>

    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>   
    </targets>
</LightningComponentBundle>

3. Then open any existing appBuilder / create a new one and drag the <useGetterSetter> in to respective column and then save and activate it.  Now click the tab to show it in browser and it will look as follows,

4. So, we are passing value of "greeting-message" property of "getterSetterExample" LWC component from "useGetterSetter" LWC component, in small letter as "hello everyone. welcome to lwc getter setter example.".
Now this message will be set in upper case in setter method of "getterSetterExample.js" file and from getter method it will return the value.
So, while calling child component (getterSetterExample) from parent component (useGetterSetter) with above message (in small letter), then system will display the message in capital letter. And the output is as follows,