A related record component is a type of component that allows users to view and edit fields from a parent record on a child record page without leaving the page. For example, a related record component can allow users to update the account status from the case layout by selecting an account record from a drop-down list.
A rich text component is a type of component that allows users to display formatted text on a record page using rich text editor tools such as bold font, bullet points, images, and links. For example, a rich text component can display a message in bold font when a case is saved as acriticalrecord type by using conditional visibility rules. References: https://help.salesforce.com/s/articleView?id=sf.
lightning_page_components_related_record.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.
lightning_page_components_rich_text.htm&type=5