# Nodes A node (as well as a [**sub-graph**](https://docs.aitheon.com/aitheon-core/main-elements/sub-graphs)) is an element of the entire system that you can connect with other elements - sub-graphs and nodes. We may think of nodes as files on a computer, that we can connect with other files and folders - sub-graphs. A node is a Core "file" with required data processing information. In other words, the node describes what to do between an [**input and an output** ](https://docs.aitheon.com/aitheon-core/main-elements/inputs-and-outputs)- it's a computer program in a particular visual form on the graph table. As an example, double-click on Item **Communications Service Sub-graph**. You will see one node inside. This is the **Communications Service Node** made to execute all the tasks of this service. Click three dots and open Settings. ![](https://11324685-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MFodfgQtPYjVLJ1kJJi%2F-MIdNlFDOgnqSpgXN-pm%2F-MIdO14p6cTvY_PXeyBm%2Fnode%20sets.png?alt=media\&token=02534041-4118-45cf-a54c-50da63613226) Unlike in a sub-graph, you are not allowed to delete inputs and outputs here. You can adjust their position on graphical representation - left or right, or both sides if you need. ### Nodes Types There are several other types of nodes: * **Provisional node** - a node you create to compose some process on the graph table, and then make a request for developers. You describe needed functions and place your request in the Marketplace for development. (See [**Add Provisional Node**](https://docs.aitheon.com/aitheon-core/aitheon-core-quick-start/add-provisional-node)). * **Mapping node** - a node you create to connect sockets that do not match (See [**Connect Nodes**](https://docs.aitheon.com/aitheon-core/aitheon-core-quick-start/create-connection)). * **Core node** - one of the ready-to-use nodes previously developed by the Aitheon team for common tasks. Stored at **Core Nodes** tab in **TOOLBOX**. * **Service node** - a ready-to-use node for a particular Aitheon service (HR, Procurement, Treasure, etc.) placed inside a related [**Service Sub-graph**](https://docs.aitheon.com/aitheon-core/sub-graphs#sub-graph-types). * **Application node** - a node made to provide any data processing under the user's control or show user real-time information about some processes and to allow this user to manage these processes with some user interface. ### Application node You can add an application to some Aitheon services. For example, a real-time chart of energy consumption. Applications are available at Marketplace; you can make a request for a new application (works same as with provisional nodes) or compose it in Aitheon's Creators Studio. When you add an application to one of your services, it will automatically appear on the main Core graph table as a node with the corresponding inscription **(1)**: ![](https://11324685-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MFodfgQtPYjVLJ1kJJi%2F-MLldJRJsxVjohNtiDe8%2F-MLlf3jjcaN__NkCYqhp%2Fapp%20node.png?alt=media\&token=fc66def5-22f8-4be6-9f5e-dd5231901da2) Click **GO TO APP (2)** to open its user interface. --- # Agent Instructions: 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: ``` GET https://docs.aitheon.com/aitheon-core/main-elements/nodes.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.