# Introduction **Catalogue** is an essential app that contains the products you want to sell on marketplaces or your e-commerce site. Regardless of being an e-commerce site or a marketplace, we call them **Channel**. A channel can only have one catalog but a catalog can be used by different channels. A catalog also has to have **Catalog Items**, **Price List**, **Stock List**, and **Category Tree** in order to be sent to its Channel. They all will be explained in later stages of this documentation. Also, there are some requirements for products to be up for sale on Channels. These requirements are as follows; * The product in the catalog has to be on the price list as well. * The product in the catalog has to be on the stock list as well. * The product has to be included at least one of the Category Nodes in the Category Tree. --- # 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://apidocs.akinon.com/omnitron/catalogue/introduction.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.