OSX Yosemite 10.10.5 won't boot after attempted Update

[iamsaintvil]

it works normally now but what does adding the "-f" to the boot list do?

 

[n3oNLit3]

According to an unreliable source in 'loads kernel caches' Below is what Ive compiled through searches

-f

.....Ignores kext caches during bootup. a kext might not have been installed properly or was (in your case) somehow 'affected', and kext cache can be damaged, and therefore become unbootable. The kext cache was replaced by the kernel cache, so theoretically, the -f boot flag should no longer work; however, this boot flag can still help.....