@pratik I'm neither a user nor the designer of the theme you're using, so I'm afraid I don't know all the differences. But a quick glance at your blog hints at posts having a prominent date at the top, compared to ordinary pages like About.

In your case, index.html is the template for the homepage. There's a particular lookup order when it comes to templates in Hugo. So, if you should happen to remove index.html, _default/list.html would take its place and be used for the homepage instead.