"io.read" is not working in ROBLOX Studio like it did on an app on my phone. Solutions?

I pasted the following code into a global script and the output says, "attempt to index global 'io' (a nil value)." It worked perfectly on the app on my phone; does io.read not exist on roblox? If so, how would I implement it?

print("Welcome to my first RPG!")
print()
print("Reply with 'start' to begin the quest and with 'end' to terminate your progress.")
print()
h = 10
r = io.read()
 
if(r == ("start"))
then
   print()
   print("Welcome to your quest! You can begin by replying with a number to select a choice.")
   print()
   print("1)Take road.")
   print("2)Wander into forest.")
   print()
   r = io.read()
 
   if(r == ("1"))
   then print()
      print("You travel the long road.")
   elseif(r == ("2"))
   then print()
      print("You begin your trek into the forest.")
   else
      print()
      print("Say a valid number.")
      repeat until r == ("1") or r == ("2")
   end
 
   print("You have ran upon a group of goblins!")
   print()
   print("You have "..h.." health remaining")
 
   print("1) Fist fight them!")
   print("2) Flee!")
   print()
   r = io.read()
 
   if(r == ("1"))
   then
      Gd = math.random(1,10)
      R = h - Gd
      print()
      if(Gd >= h)
      then
         print("You took "..Gd.." damage. You have been defeated.")
      else
         print("You take "..Gd.." damage, but still manage to fight them off with "..R.." health remaining!")
      end
   elseif(r == ("2"))
   then print()
      print("You run to the nearest river and you are all out of stamina. You can't run for much longer anytime soon.")
 
   elseif(r == ("end"))
   then
      print()
 
   else print("You must say something valid. Please restart the script.")
   end
 
   if(r == ("end"))
   then print()
      print("You have ended your quest. Please restart the script to begin again.")
   end
end