> For the complete documentation index, see [llms.txt](https://shopify-1.gitbook.io/typescript/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shopify-1.gitbook.io/typescript/introduction/what-is-typescript.md).

# What is TypeScript?

TypeScript is a statically typed superset of JavaScript. It provides optional static typing, classes, and interfaces. It also enables a number of ES.Next features to be used, without requiring use of another transpiler (such as [Babel](https://babeljs.io/)).

If you are already familiar with ES6 (or beyond), then congrats!—you are already well on your way to understanding the TypeScript syntax. If not, we recommend [familiarizing yourself with ES6](https://github.com/ericdouglas/ES6-Learning) beforehand to get the most out of TypeScript.

## The TypeScript type system

### What is static typing?

A language is said to be **statically typed** if the type of a variable is known at compile time. Some examples include C#, Rust, TypeScript.

A language is said to be **dynamically typed** if the type of a variable is known only once its run-time value is known. Examples: Ruby, Python, JavaScript.

### Types are optional

TypeScript's optional typing is one of its more powerful and unique features.

Other statically typed languages like C# or Java require you to specify the type of the variable when declaring it.

For example, to declare a string in C#, the `string` type must be specified:

```c
string name = "Bonjour";
```

In TypeScript, declaring the type is completely optional. So both are valid:

```typescript
const name = "Bonjour";
```

or

```typescript
const name: string = "Bonjour";
```

Takeaway: types are **explicit** *or* **implicit**. We'll dive deeper into TypeScript's ability to [infer types](/typescript/beginner/inference.md) later on.

### Duck typing

One of TypeScript’s core principles is that type-checking focuses on the *shape* that values have. This is often called "duck typing" or "structural subtyping".

We'll look more closely at how TypeScript uses duck typing in the section on [Interfaces](https://github.com/shopify/typescript/tree/9613b2fbeb75125a3b75af1f88bee26f07071d04/docs/docs/interfaces.md).

## ES.Next

While the main focus of this guide is to cover TypeScript's *unique* features, TypeScript also provides a number of features that are planned in ES6 and beyond. The TypeScript team is actively adding these features, and the list continues to grow.