fastboot devices shows nothing but ADB has full access

So I recently installed adb and fastboot via apt-get android-tool-adb and android-tools-fastboot. I am having trouble with fastboot detecting my device. When I run fastboot I get command not found and when I runt fastboot devices I get new line and no detected device. If anyone has any info on this please assist me in correcting this. When I use "adb" devices I get

928@penguin:~$ adb devices
List of devices attached
43e56835 device

and when I run "fastboot devices" I get

928@penguin:~$ fastboot devices
928@penguin:~$

Also when I run "fastboot flash twrp.img" i get

928@penguin:~$ fastboot flash twrp.img
< waiting for any device >

Any info is highly appreciated