Physical location of components
All components are stored in the /bitrix/components/ folder. The system components are in the /bitrix/components/bitrix/ folder. The content of this folder is updated by the update system and must not be modified by users.
Users can store their own components in any subfolder of /bitrix/components/, or in the /bitrix/components/ root.
The name of a subfolder in /bitrix/components/ is the component namespace. For example, all system components belong to the bitrix namespace. When creating a custom component, you should create a namespace and put custom components there.
For example, a system component news exists located in the bitrix namespace. If you need a custom news component implementing functions unavailable in the standard system component, you should create a namespace (subfolder) in /bitrix/components/ (for example, demo) and put the custom component news there. The two components news will be available in different namespaces: bitrix:news and demo:news; both of them will be shown in the component tree in the visual editor.
The component names have the format identifier1.identifier2.... For example: catalog, catalog.element, catalog.section.list etc. A good idea is to create hierarchical names, from common to particular, e.g. catalog.section.elements for a component that would display a list of products of a certain group. Global components (that reside out of namespace) do not specify the namespace.