The Jaxx Classic wallet native app for computers (not including Google Chrome) stores the app configuration files on the computer's hard-drive. This includes an encrypted version of your wallet's Backup Phrase.
The data location in which Jaxx Classic stores your wallet information depends on the operating system you are using:
MacOS: /Users/[username]/Library/Application Support/Jaxx/
Windows: C:\Users\<Your Computer's User Name>\AppData\Roaming\Jaxx\
There are two purposes you may need to know the above locations:
1. If you want to completely wipe the Jaxx Wallet and its files of your computer
2. If you've lost access to your computer (maybe due to a hardware malfunction) but have a copy of your hard-drive data and could potentially use the backed up folder data of the Jaxx Classic wallet to recover access to your wallet on a new computer.