where to use these sorting techniques? what conditions demand each of them?
some article will help
where to use them: anywhere you need the information arranged in some logical fashion, such as listing people alphabetically by their last and first names.
Those are just different algorithms that do the same thing -- sort. You could use any of them for any given task, although some might do it faster than others. There is no "right one for the right job" sort of thing. Use any algorithm you want.