Everything after the hyphen is an explanation
cd /dev – devices
ls -lah – lists all devices connected to the system
jstest and the device name, i.e., js0 or the full path from anywhere else /dev/input/js0
The -lah means
-l long format, displaying Unix file types, permissions, number of hard links, owner, group, size, last-modified date and filename
-a lists all files in the given directory, including those whose names start with “.” (which are hidden files in Unix). By default, these files are excluded from the list.
-h print sizes in human readable format