> For the complete documentation index, see [llms.txt](https://swlaschin.gitbook.io/fsharpforfunandprofit/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swlaschin.gitbook.io/fsharpforfunandprofit/understanding-f/understanding-fsharp-types.md).

# The "Understanding F# types" Series

F# is not just about functions; the powerful type system is another key ingredient. And just as with functions, understanding the type system is critical to being fluent and comfortable in the language.

In addition to the common .NET types. F# has some other types that are very common in functional languages but not available in imperative languages like C# or Java.

This series introduces these types and how to use them.

* [Understanding F# types: Introduction](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/types-intro.md). A new world of types.
* [Overview of types in F#](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/overview-of-types-in-fsharp.md). A look at the big picture.
* [Type abbreviations](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/type-abbreviations.md). Also known as aliases.
* [Tuples](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/tuples.md). Multiplying types together.
* [Records](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/records.md). Extending tuples with labels.
* [Discriminated Unions](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/discriminated-unions.md). Adding types together.
* [The Option type](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/the-option-type.md). And why it is not null or nullable.
* [Enum types](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/enum-types.md). Not the same as a union type.
* [Built-in .NET types](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/cli-types.md). Ints, strings, bools, etc.
* [Units of measure](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/units-of-measure.md). Type safety for numerics.
* [Understanding type inference](/fsharpforfunandprofit/understanding-f/understanding-fsharp-types/type-inference.md). Behind the magic curtain.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://swlaschin.gitbook.io/fsharpforfunandprofit/understanding-f/understanding-fsharp-types.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.