The Guided Application Creator (GAC) is a tool that helps you create applications on the ServiceNow platform by guiding you through the steps of defining the data model, user interface, and logic. When using the GAC, you can designate data tables in three ways:
* Upload an existing PDF: You can upload a PDF file that contains the table schema and sample data.
The GAC will parse the PDF and create the table and fields based on the file content.
* Create a new table on the platform: You can create a new table on the platform by specifying the table name, label, and description. You can also add fields, indexes, and relationships to the table using the GAC.
* Upload an existing spreadsheet: You can upload a spreadsheet file that contains the table schema and sample data. The GAC will parse the spreadsheet and create the table and fields based on the file content.
The other options are not valid ways to designate data tables when using the GAC. You cannot upload an existing word processing document or use a freeform database. You can use an existing table on the platform, but you cannot designate it as a data table. You can only use it as a reference table for lookup fields.
References:
Guided Application Creator
Create a table from a PDF or spreadsheet
Create a table from scratch

"Schema map: Provides a graphical representation of the relationships between tables."
https://docs.servicenow.com/bundle/tokyo-platform-administration/page/administer/table-administration
/concept/c_TableAdministration.html

The ServiceNow REST API is a web service that allows you to interact with the ServiceNow platform using HTTP requests and responses. The ServiceNow REST API supports the following methods:
POST: This method allows you to create a new record or execute an action on the ServiceNow platform. For example, you can use the POST method to create an incident or run a script.
GET: This method allows you to retrieve information from the ServiceNow platform. For example, you can use the GET method to get the details of a user or a table.
DELETE: This method allows you to delete a record or a resource from the ServiceNow platform. For example, you can use the DELETE method to delete an attachment or a workflow context.
PUT: This method allows you to update a record or a resource on the ServiceNow platform. For example, you can use the PUT method to update the state of a task or the value of a system property.
PATCH: This method allows you to update a record or a resource on the ServiceNow platform by sending only the changes. For example, you can use the PATCH method to update the short description of an incident or the order of a module.
The method COPY is not part of the ServiceNow REST API. There is no COPY method in the HTTP protocol. To copy a record or a resource on the ServiceNow platform, you need to use the POST method with the clone action.
References:
ServiceNow REST API overview
ServiceNow REST API methods
[ServiceNow REST API actions]

Inbound email matching uses Watermarks and Subject lines (with record numbers like INC0010001) to associate emails with existing records.
From Email Handling Docs:
"ServiceNow uses Watermark IDs and subject lines containing record numbers to find the corresponding task or record when processing inbound email."

"There are two possible ways to respond to events:
- Email Notification
- Script Action" - see this quote in link below:
https://developer.servicenow.com/dev.do#!/learn/learning-plans/tokyo/new_to_servicenow
/app_store_learnv2_automatingapps_tokyo_responding_to_events