JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="index-controls">
    <li>
        <div id="1" class="link active">FREE DISC Profile</div>
        <ul>
            <li>
                <h2>Training that fits like a glove</h2>
            </li>
            <li>
                <p>Your company is as individual as the people it employs; and as such, it’s likely that your training requirements don’t tick any one, particular box. You may currently have a personnel issue that requires urgent attention. Or, you are taking a serious look at the management strategies you use to run your organisation and are considering an overhaul.</p>
            </li>
        </ul>
    </li>
    <li>
        <div id="2">Last Minute Availability</div>
        <ul>
            <li>
                <h2>Training that fits like a glove</h2>
            </li>
            <li>
                <p>Your company is as individual as the people it employs; and as such, it’s likely that your training requirements don’t tick any one, particular box. You may currently have a personnel issue that requires urgent attention. Or, you are taking a serious look at the management strategies you use to run your organisation and are considering an overhaul.</p>
            </li>
        </ul>
    </li>
    <li>
        <div id="3">Bespoke Training</div>
        <ul>
            <li>
                <h2>Training that fits like a glove</h2>
            </li>
            <li>
                <p>Your company is as individual as the people it employs; and as such, it’s likely that your training requirements don’t tick any one, particular box. You may currently have a personnel issue that requires urgent attention. Or, you are taking a serious look at the management strategies you use to run your organisation and are considering an overhaul.</p>
            </li>
        </ul>
    </li>
</ul>

CSS

.active {
    
    background-color: #CCC;
    
}

JavaScript

var list = $('#index-controls li div');
list.click(function() {
    list.removeClass('active');
    $(this).addClass('active');
});