By default, files are sorted clockwise by decreasing file size. From the View menu, you can set a different Size Mode.
Size
The default. You can quickly find files that take away most of your disk space.
Size on Disk
When opening an ordinary directory, this setting will produce a similar display as for Size (since usually there is only a small difference between the file size and the file size on disk, or allocated file size). When scanning a directory managed by a cloud service, this setting will effectively hide all those files that are not downloaded locally (since their allocated file size is 0 bytes).
Child Count
Directories are sorted by the number of subfiles, followed by all the regular files sorted in alphabetical order. This mode allows to find directories with many files that may slow down some operations: for example, copying or syncing a directory containing many files is often slower than copying a directory with less files but the same overall size.