Let Me just refresh it so you can see that I get an error here because, we have already declared a constant, value for age which is and, again, we are changing the value to 21, so, this will definitely give, you an error that is the uncaught, type error assignment. To constant, variable, so, here your variable, age is a constant, you cannot, assign any other value, to this variable anywhere, so, that it will show you an error so. Basically, we cannot reassign, a constant. So. Once you have used constant. You cannot change the value so, the best practice, is to use where, whenever, you are planning to change the value next so. Now that you know what are variables, and what are constants, you must be wondering, what are the kind of values, that we can assign to these variables. So. Now let's move ahead and have a look at the different data types that you can use so. Now here we have two different types so, first we have the primitive, or the value types and then, we have the reference types, first, we will have a look at the different primitive, types now. The data types are basically, the type of data that can be used and manipulated in a program, so, the different data types include, the numbers, strings, boolean, undefined. And null so. Now talking about these data types let's go back to our code and see what our string literals, what our numbers what our boolean. So. Let's, just type let name. Equals. To Ed Eureka. Then, we have another variable, as age which is equals, to suppose, 23. Now. For checking boolean. That just, give another, variable. As is approved. Is. Equals. To true so. True and. False are the ones that represent, our boolean, values. So. This one is basically our, string, literal, and, this. One is our, number, literal. This. One we are using for, boolean. Next. Up if we just write let. First, name, and, put. A semicolon, it automatically. Gives an undefined. Value to this one but, we can also write. It as first. Name is equals to undefined. So. There's basically no value assigned to this particular variable. Now, the final one is the null value, so. Let me just give it as let date, equals, to null. So. Now let me just save this and then, let me go back to my console, again now, once i refresh it so. Basically I have not given any console, here so there's no output in my console, but then you, can always check, the type of your literals, here so, what I have to do is just type time. Off and, then, if I want to check the type of my, variable. Name so, I can just give name and it, shows me string, so. Here I have my. Name as I do Rica which is a string literal so, this is exactly the value that it is showing me here that is the type of my name is string now. Let's check the type, of age. So. You can see that it shows number. So, my age declares, my number. Literal, here in the, same way when we type type of is approved, pause, I write type of is. Approved. It'll show me boolean, so. You can see that inside the console itself you can find out the types of all of these variables.