\usepackage{tocloft}
\begin{document}
\fontsize{14}{14}\selectfont {\tableofcontents{}}
\end{documents}


Contents

1. Introduction 1
2. Review of literature 3

I want to put "Page" over page numbers, "Sno." over numbers and "Description" over the section name. I am unable to find any similar relevant question here. Can anyone help me with that?

It would have been very helpful to provide an MWE (from \documentclass... to \end{document}) that showed your problem. The ToC you displayed was certainly not produced by the code snippet you posted.

As I have no idea what you have done the MWE below is based in the normal ToC layout but with your column names printed.

% tocheadsprob.tex  SE 576103

\documentclass{article}

\usepackage{tocloft}
\begin{document}
\renewcommand{\cftaftertoctitle}{%
\\[\baselineskip]Sno Description \hfill Page}
\fontsize{14}{14}\selectfont {\tableofcontents{}}

\section{Introduction}
\clearpage
\section{Review}

\end{document}


This should give you an idea of how you can meet your desired layout but you will have to configure the layouts to suit your vision.