What templating engine does Magento 2 use for it's Javascript widgets

[OliverRC]

Is there an existing issue for this?

• I have searched the existing issues

What's missing?

• For example in the guide https://developer.adobe.com/commerce/frontend-core/javascript/jquery-widgets/breadcrumbs/#result
• Template breadcrumbs.html

<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<ul class="items">
<% _.each(breadcrumbs, function(crumb) { %>
    <li class="item <%- crumb.name %>">
        <% if (crumb.link) { %>
        <a href="<%= crumb.link %>" title="<%- crumb.title %>"><%- crumb.label %></a>
        <% } else if (crumb.last) { %>
        <strong><%= crumb.label %></strong>
        <% } else { %>
        <%= crumb.label %>
        <% } %>
    </li>
<% }); %>
</ul>

What templating engine is this, where can we lookup the syntax documentation?