For a manually-formatted bibliography, there is no need to have citations - \cite - within the document.
This environment sets the scope for the actual bibliography. It defines a list-like environment within which you can use \bibitem to set a bibliography item.
The thebibliography environment takes a single argument that represents the widest element to be expected in the enumeration of the \bibitems. For less than 10 entries, use a single character/digit; for less than 100 entries, use two characters/digits, ...
Set the bibliography item <b> and make it available to \cite within the document using the label <a>.