I've found this annoying problem where if I press function keys they don't perform as expected. F12 opens up Chrome's inspector while F11 just hides windows to show desktop.
The only way I can click to say change brightness is to click the FN key.
What is causing this and how do I change it back to standard function key functionality? And what causes it in the first place?
You can set which way this behaves in System Prefs > Keyboard > Keyboard
'Use F1, F2, etc. keys as standard function keys'
Whichever way you choose, holding Fn/F-key will activate the opposite mode temporarily.
This pref pane has changed appearance slightly over the years, but the functionality remains the same up to Monterey, but it has moved in Ventura.
from Apple KB
macOS Ventura
Choose Apple menu > System Settings.
Click Keyboard in the sidebar.
Click the Keyboard Shortcuts button on the right.
Click Function Keys in the sidebar.
Turn on "Use F1, F2, etc. keys as standard function keys".
On a Macally keyboard I've found that holding Fn and pressing Esc will "lock" the fn key allowing me to use the Function keys by default. Without this, even having set the "Use F1, F2 keys etc..." it wasn't working without holding the Fn key. Locking it worked like a charm.
Cmd + Shift + F
Above command will toggle the task-bar. Coming from a Windows OS, this was the combination I was looking for to mimic Fn + F11.
As well as enabling the "Use F1, F2, etc" option, you may also want to un-bind the F11 key from the "Show Desktop" feature.
