What does the up arrow icon mean?

What does the up arrow mean on the top?
I pull down the screen to see but there's nothing there?

Capital letter indicator.

I also notice that it seems to appear when I have just sent a text. But I would go with capital letter indicator also.

when you are in a text field, the arrow will show up indicating capital letter. if you press the shift key on your keyboard, it'll go away, and start typing with small letter.

...and if you hold Shift, the arrow will go solid; indicating caps lock.

(Hint: actionable notifications appear on the top left, status indicators appear on the right).

Just a hint…

By default any text field you'll be on that can start with capital (upper case) will have that icon shown. It's basically stating you have Shift pressed (like guys who has posted above).

Similarly you'll see an Alt icon when Alt is pressed.

What is a STRG key?

Originally Posted by Edietel

What is a STRG key?

German keyboard. Steuerung (STRG) or control key. Also note where the Y key is located.

umm, duh, sorry for the stupid question!
Didn't even think about it looking exactly like the shift key.

Originally Posted by Andreabb

umm, duh, sorry for the stupid question!
Didn't even think about it looking exactly like the shift key.

Don't be sorry! I learnt a new German word as a result LOL

There is no such thing as a stupid question, only a stupid answer. We all learn daily. Feel free to ask whatever you dont understand.