why do I need <br />

Question

why do I need <br /> in the flowing?
<table border="2">
<tr>
<td>Red</td>
<td>Blue</td>
<td>Green</td>
</tr>
<tr>
<td><br /></td>
<td colspan="2"><br /></td>
</tr>
</table>

Answer 1

In HTML, the <br> tag is used for line break. It is an empty tag i.e. no need to add an end tag. Writing <br> tag is perfectly fine.
Let’s see the usage of other br tags i.e. <br/> or <br />,
In HTML, use <br> tag.
In XHTML, the valid way is to use <br/> or <br></br> as mentioned in the XHTML guidelines.(https://www.w3.org/TR/xhtml1/#h-4.6)
According to w3 guidelines,(https://www.w3.org/TR/xhtml1/#guidelines) a space should be included before the trailing / and > of empty elements, for example, <br />. These guidelines are for XHTML documents to render on existing HTML user agents.

Answer 2

looks same to me with or without <br />

Answer 3

<br/> means line break.