| #https://www.notion.so/n8n/Frontmatter-432c2b8dff1f43d4b1c8d20075510fe4 | |
| contentType: overview | |
| # Data item linking | |
| An item is a single piece of data. Nodes receive one or more items, operate on them, and output new items. Each item links back to previous items. | |
| You need to understand this behavior if you're: | |
| * Building a programmatic-style node that implements complex behaviors with its input and output data. | |
| * Using the Code node or expressions editor to access data from earlier items in the workflow. | |
| * Using the Code node for complex behaviors with input and output data. | |
| This section provides: | |
| * A conceptual overview of [Item linking concepts](/data/data-mapping/data-item-linking/item-linking-concepts.md). | |
| * Information on [Item linking for node creators](/data/data-mapping/data-item-linking/item-linking-node-building.md). | |
| * Support for end users who need to [Work with the data path](/data/data-mapping/data-item-linking/item-linking-code-node.md) to retrieve item data from previous nodes, and link items when using the Code node. | |
| * Guidance on troubleshooting [Errors](/data/data-mapping/data-item-linking/item-linking-errors.md). | |