br在html中的语义是什么？

var oldText = @"<p><i>This is</i> some sample text to <strong>demonstrate</strong> the capability of the <strong>HTML diff tool</strong>.</p>
<p>It is based on the <b>Ruby</b> implementation found <a href='http://github.com/myobie/htmldiff'>here</a>. Note how the link has no tooltip</p>
<p>What about a number change: 123456?</p>
<table cellpadding='0' cellspacing='0'>
<tr><td>Some sample text</td><td>Some sample value</td></tr>
<tr><td>Data 1 (this row will be removed)</td><td>Data 2</td></tr>
</table>
                    Here is a number 2 32
<br><br>
                    This date: 1 Jan 2016 is about to change (note how it is treated as a block change!)";

var newText = @"<p>This is some sample <strong>text to</strong> demonstrate the awesome capabilities of the <strong>HTML <u>diff</u> tool</strong>.</p><br/><br/>Extra spacing here that was not here before.
<p>It is <i>based</i> on the Ruby implementation found <a title='Cool tooltip' href='http://github.com/myobie/htmldiff'>here</a>. Note how the link has a tooltip now and the HTML diff algorithm has preserved formatting.</p>
<p>What about a number change: 123356?</p>
<table cellpadding='0' cellspacing='0'>
<tr><td>Some sample <strong>bold text</strong></td><td>Some sample value</td></tr>
</table>
                    Here is a number 2 <sup>32</sup>
<br><br>
                    This date: 22 Feb 2017 is about to change (note how it is treated as a block change!)";

var diffHelper = new HtmlDiff.HtmlDiff(oldText, newText);
litOldText.Text = oldText;
litNewText.Text = newText;

// Lets add a block expression to group blocks we care about (such as dates)
diffHelper.AddBlockExpression(new Regex(@"[\d]{1,2}[\s]*(Jan|Feb)[\s]*[\d]{4}", RegexOptions.IgnoreCase));

litDiffText.Text = diffHelper.Build();

/* ***************************************
** Diff related styles
*****************************************/

ins {
background-color: #cfc;
text-decoration:inherit;

}

del {
color: #999;
background-color:#FEC8C8;
}

ins.mod {
background-color: #FFE1AC;
}