An HTML element is specified by a start tag. If the element comprises the other content, it closes with an end tag, where the element name is defined by a forward slash, you can see below the tags:
<p> </p> => This is paragraph content.
<h1> </h1> => This is heading content.
<div> </div> => This is division content.
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So, the above HTML elements have end tags, but, there are a few HTML elements which don't require to be closed, such as <img.../>, <hr /> and <br /> elements.
These are called as void elements.