The default scope for a serialization in Sitecore Content Serialization (SCS) includesall the content itemsunder the specified path andall their descendants1.You can configure what and how content items are included and excluded from serialization in a module file such as Project.module.json1.You can also use rules to configure the serialization of content item trees with different scopes1.
References:
Sitecore Content Serialization structural overview
The default serialization format