What is the difference between declaring variables with 'var' and 'val' in Kotlin?

In Kotlin, var and val are used to declare variables, but they have a fundamental difference:

• var declares a mutable variable. The value of such a variable can be changed after initialization.
• val declares an immutable variable, similar to a constant. Its value cannot be changed after assignment.

Example:

var mutableVar = 10
mutableVar = 20  // allowed

val immutableVal = 30
// immutableVal = 40  // compilation error

Using val is recommended when the value should not change, as it increases code safety and readability.