What happens when i put "data" as class in a div tag

<div class="data">
Lorem ipsum dolor sit amet consectetur adipisicing elit. Impedit odit labore ratione in perferendis perspiciatis repellendus fugit? Molestiae incidunt autem eum? Accusamus dignissimos facere consequuntur beatae assumenda? Numquam, nam a.

</div>

above code shows this as output :

Lorem ipsum dolor sit amet consectetur adipisicing elit. Impedit odit labore ratione in perferendis perspiciatis repellendus fugit? Molestiae incidunt autem eum? Accusamus dignissimos facere consequuntur beatae assumenda? Numquam, nam a. // = 0 ? '&' : '?') + '_cacheOverride=' + (new Date().valueOf()); } parent.appendChild(elem); } } var protocol = window.location.protocol === 'http:' ? 'ws://' : 'wss://'; var address = protocol + window.location.host + window.location.pathname + '/ws'; var socket = new WebSocket(address); socket.onmessage = function (msg) { if (msg.data == 'reload') window.location.reload(); else if (msg.data == 'refreshcss') refreshCSS(); }; if (sessionStorage && !sessionStorage.getItem('IsThisFirstTime_Log_From_LiveServer')) { console.log('Live reload enabled.'); sessionStorage.setItem('IsThisFirstTime_Log_From_LiveServer', true); } })(); } else { console.error('Upgrade your browser. This Browser is NOT supported WebSocket for Live-Reloading.'); } // ]]>

can anyone explain what is happening here and what is the meaning of data class in html. is it reserved or have i made some other mistake.