How to display text inside an input filed

<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
<style>

</style>
</head>
<body>
<input type='text' value='some text' size='100'/>
<p>
<input onclick='this.value="some text again";' type='text' value='click inside to display the new text' size='100'/>


<script>

</script>
</body>
</html>