What the use of Canvas Element in HTML5?

The canvas element is used to  draw graphics images on a web page by using javascript like below

<canvas id="pcdsCanvas" width="500" height="400">
</canvas> 
<script type="text/javascript">
           var pcdsCanvas=document.getElementById("pcdsCanvas");
           var pcdsText=pcdsCanvas.getContext("2d");
           pcdsText.fillStyle="#82345c";
           pcdsText.fillRect(0,0,150,75);
</script>