Application binaries usually installed into /bin or /usr/bin folders.
You could use ls /bin or ls /usr/bin to list all binaries to console commands and desktop applications.
Also, if you have your Firefox running, you could use ps aux | grep firefox command to see what binary path have been used for application.
For example:
$ ps aux | grep chrome
user 11182 0.0 0.6 4568428 54112 ? SNl 13:48 0:00 /opt/google/chrome/chrome --type=renderer --disable-webrtc-apm-in-audio-service --field-trial-handle=7356609730568785120,9558563176934852878,131072 --lang=en-US --enable-crash-reporter=181c2763-8134-47a2-bc44-349a4e81270e, --disable-client-side-phishing-detection --enable-auto-reload --num-raster-threads=1 --renderer-client-id=16 --no-v8-untrusted-code-mitigations --shared-files
It shows that chrome binary is located in /opt/google/chrome/ folder. So another location you could check is /opt: ls /opt.
Console commands for applications usually named starting with lower case letters.