A function typically has its code wrapped in braces ({ }).

However, simple functions can use "expression body" syntax, with a single statement (preceded by =) forming the body. When you call that function, the statement is executed and whatever it evaluates to is what the function returns.

This saves you a return keyword. Plus, as with variables, Kotlin can infer the data type that the function returns (in many cases), saving you having to declare the type manually.

• the documentation
• Elements of Kotlin