This is a very basic but I have been unable to find the answer on the web.
Is it possible to
git rm, i.e. to remove a tracked file, from magit?
Magit does not provide a command that does
git rm (but if you opened a feature request, then I would probably add it eventually).
Meanwhile you can delete the file using some other method, e.g. using M-x delete-file RET <file> RET. Once you have done that refresh the Magit buffer using g and then stage the "deletion" of the file by moving to it in the list of unstaged changes and then pressing s.