what is a substring in toc code example

Example 1: What is CanCollide in roblox?

-- CanCollide is command a that will be able to make a Part collide or not

-- To make an object not fall off a part 
script.Parent.CanCollide = true

-- To make an object fall off a part
script.Parent.CanCollide = false

Example 2: what is monad in javascript

function Identity(value) {
    this.value = value;
}

Identity.prototype.bind = function(transform) {
    return transform(this.value);
};

Identity.prototype.toString = function() {
    return 'Identity(' + this.value + ')';
};