the differences between val var and def

I was wondering about the differences between val, var and def in Scala, and these are what I found :

• def

  1. Immutable
  2. Lazily evaluated (Evaluated by Name)

  scala> def x = 1+2
  x: Int
  scala> x = 4
  
  
  <console>:11: error: value x_= is not a member of object $iw
         x = 4  //can't reassign x because immutable
         ^
  
  
  scala> x        //Lazily evaluated 
  res0: Int = 3
  
  
  

• val

  1. Immutable
  2. Eagerly/immediately evaluated (evaluated by value)

  scala> val x = 1+2 
  x: Int = 3    // Eagerly/immediately evaluated
  
  
  scala> x = 4    //can't reassign x because immutable
  <console>:11: error: reassignment to val
     x = 4
       ^
  
  
  

• var

  1. mutable
  2. Eagerly/immediately evaluated (evaluated by value)

  scala> var y = 3
  y: Int = 3  // Eagerly/immediately evaluated
  
  
  scala> y = 2    //can reassign value
  y: Int = 2
  

Hope these help,,thanks