Want some explanation

Question

I'm asking again as my first question was mistyped
Can you please elaborate "function(function(arg))" from the given example
Def applytwice(function,arg):
Return function(function(arg))
Def addfive(x):
Return x+5

Print(applytwice (addfive,10)

Output is 20

Can you explain why it is adding 10 to 10
I'm new in py . Sorry for wrong capitalized words as autocorrect sucks .
Thanks for reading

Answer 1

applytwice(addfive, 10)

in applytwice,
addfive(addfive(10)) = addfive(10 + 5) = addfive(15) = 5 + 15 = 20