Val and Var in Kotlin

Variables defined with var are mutable(Read and Write)
Variables defined with val are immutable(Read only)

Simply, var (mutable) and val (immutable values like in Java (final modifier)

var x:Int=3
x *= x

//gives compilation error (val cannot be re-assigned)
val y: Int = 6
y*=y

val and var both are used to declare a variable. 

var is like general variable and its known as a mutable variable in  

kotlin and can be assigned multiple times.   

val is like constant variable and its known as immutable in 

kotlin and can be initialized only single time.