With the help of the standard environment thebibliography a bibliography can be created manually. The question whether a bibliography should be created manually or automatically cannot be answered in general. There are good reasons why one or the other should be used. If, for example, it is foreseeable that documents from a certain subject area will be worked on again and again, and thus also with similar or the same sources, an automated variant is usually to be preferred. If, however, it is only a unique text and there is no style for the requirement of the design of the bibliography, the manual variant can be better.
The thebibliography environment provides space for a bibliography. max label defines how deep the entries should be indented. The command \bibitem creates an entry marked with the label, if the label is missing a number is inserted. The quote abbreviation should consist of numbers and letters, commas are not allowed. Citations / Quotations are made with \cite{citation / quotation abbreviation} in the document.
\begin{thebibliography}{max label} \bibitem[label]{citation / quotation abbreviation} Author, title etc... ... \end{thebibliography}
One of the advantages of manual creation is that the design of the citation in the document and the appearance of the bibliography can be changed. An example that I regularly mention is "framed with pink hearts and in green letters" by me.
Bibliography\documentclass{article} ... \usepackage{ifthen} \usepackage{xcolor} \usepackage{arev} \makeatletter \renewcommand\@cite[2]{% $\textcolor{pink}{\varheart}$~\textcolor{green}{#1}~$\textcolor{pink}{\varheart}$\ifthenelse{\boolean{@tempswa}} {,\nolinebreak[3] #2}{} } \renewcommand\@biblabel[1]{\textcolor{green}{#1}} \makeatother \begin{document} ... I regularly mention is "framed with pink hearts and in green letters" \cite{citation}. ... ... \begin{thebibliography}{max label} \bibitem[by me]{citation} I, in almost every course of the last 10 years etc... \end{thebibliography} \end{document}
With the command \renewcommand{\refname}{bibliography} the literature can be renamed, for example in article class, from References to bibliography.
The command \cite[option]{citation / quotation abbreviation} quotes.
A disadvantage of a manual bibliography is that the entire set bibliography is simply output without the compiler checking whether the respective sources were also used in the document. But the author / creator should know this.
With the help of BiBTeX or BiBLaTeX bibliographies can be created automatically. However, a literature database and a suitable style are necessary for this. The literature database contains the entries of the sources and the style determines both the appearance of the quotation in the text and the appearance of the bibliography in the document.