You can use let statements to create variables, but you need to specify the type in creation, either implicitly or explicitly.

// creates a variable with an implicit integer type
let x = 3

// creates a variable with an explicit integer type
let y: int = 3

You modify a variable via assignment:

let lel = 3

lel = 4

Function perameters are also variables, and can be given explicit types as well.

func heck(a: int, b: int) {
    //code
}

Variables can be declared with any data type.