What does -> mean in F#?

let f : int -> int = ...

fun x y -> x + y + 1

match someList with
| [] -> 0
| h::t -> 1

> List.map (fun x -> x % 2 = 0) [1 .. 10];;
val it : bool list
= [false; true; false; true; false; true; false; true; false; true]

match x with
| 1 -> dosomething
| _ -> dosomethingelse

> let add a b = a + b
val add: int -> int -> int

> let inc = add 1
val inc: int -> int

val f : (int -> int) = fun n -> n * 2

adder n x y = n + x + y

adder 1 2 3

adder :: Int -> Int -> Int -> Int

five :: Int
five = 5

add5 = adder 5

add5 :: Int -> Int -> Int

addder :: Int -> (Int -> (Int -> Int))

add5andtwomore :: Int -> (Int -> Int)
add5andtwomore = adder 5

add5and7andonemore :: Int -> Int
add5and7andonemore = adder 5 7

> add5and7andonemore 9
 => ((add5andtwomore) 7) 9
 => ((adder 5) 7) 9)
<=> adder 5 7 9

> adder 5 7 9 = 5 + 7 + 9
 => 5 + 7 + 9
 => 21

> 5 + 7 + 9
 => (+ 5 (+ 7 9))
 => (+ 5 16)
 => 21

fun x y -> x + y + 1

(x, y) => x + y + 1;

Int -> Int -> Int

Int -> (Int -> Int)

F#: let f = fun x -> x*x
C#: Func<int, int> f = x => x * x;

let isOne x = match x with
 | 1 -> true
 | _ -> false