There are many different types of Atoms in XPOR, each of which is provided with its' own dedicated Help resource. They are deployed on Templates, to provide their function, e.g. a Menu or a Shopping Basket. They can be set as a "default", when you create or modify a Template with Object modeller. They can also be set and changed directly on the web page you have created with a template.
Finally, XPOR allows you to reset a web page to its' default Atom settings (PULL) AND set the default Template atoms / configuration to the settings you have configured on a web page (PUSH)
For a full description of Atoms and their use on Templates, please refer to the Templates Help resource