I am getting the error shown in the attached photo, Please guide me to fix it. I am using overleaf site to write the paper.
>Solution :
TeX is case sensitive. Use
\textbf{...}
However to follow latex’s principle to separate formatting and content, it would be better to not manually mess with the fonts like this. Instead your use-case seems to be better suited for a sectioning command like \subsection{...}, or whatever level you like.