> For the complete documentation index, see [llms.txt](https://www.learnros2.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.learnros2.com/ros/navigation-and-planning/navigation2-implementation-overview.md).

# Navigation2 Implementation Overview

## Input to the navigation stack.

In ROS2, there are three types of input: (1) topics, (2) service calls, and (3) actions. In this section, we will focus on the topics.

| Component                            | Topics | Message Type             |
| ------------------------------------ | ------ | ------------------------ |
| nav2\_costmap\_2d::CostmapSubscriber |        | nav2\_msgs::msg::Costmap |
|                                      |        |                          |
|                                      |        |                          |