Added more to semantic elements (#2637)

I think the already given description was not enough for new learners, so I added a little more about what semantic elements in HTML are and what they do.

content/roadmaps/100-frontend/content/101-html/101-writing-semantic-html.md

@@ -1,6 +1,6 @@
 # Semantic HTML
 
-Semantic element clearly describes its meaning to both the browser and the developer.
+Semantic element clearly describes its meaning to both the browser and the developer. In HTML,semantic element are the type of elements that can be used to define different parts of a web page such as <form>, <table>, <article>, <header>, <footer>, etc.
 
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 <BadgeLink badgeText='Read' colorScheme='yellow' href='https://developer.mozilla.org/en-US/docs/Glossary/Semantics'>Semantics - MDN Web Docs Glossary: Definitions of Web-related terms | MDN</BadgeLink>