How are paths to files and folders constructed in OS X? I need to indicate a right file path to read a .csv file into R on OS X, but how can I find where the file is stored? Looking at Excel files, the file path starts at users/…, but there is no indication of a disk or something.
There's no disk letter in OS X unlike Windows.

The mount point for disks is usually /Volumes. For example, files on a flash drive with the name FLASHDRIVE will be located in /Volumes/FLASHDRIVE/.

The startup disk is the root, /. Therefore, the Users folder is /Users. No drive letter is prepended to this.