There are really only two situations where it matters. One is in developing tooling; you have to understand how all this works together so that the user can do things like call `summary` or `plot` on your objects.
The other is when you are trying to debug why something isn't working -- a lot of the time you can dump an R function just by typing the name, so you can run `table` with no parameters to get the `table()` function, if you're trying to figure out why it's not working right for your data. But if you execute `plot` you'll get some thing saying "UseMethod("plot")" which feels a bit recursive -- "in order to plot, plot", and then you end up going down that rabbit hole, which leads you to contributing to R packages, developing some of your own, and eventually posting on HN about how R's class system works.
