https://developer.servicenow.com/dev.do#!/reference/api/rome/client
The GlideUser object (g_user) is part of the client-side scripting API that provides information about the current user and the user's preferences. It can be used in Client Scripts and UI Policies to customize the user interface based on the user's role, language, time zone, etc. The workflow.scratchpad object is only available in Workflow scripts, which are used to automate processes on the platform. The current and previous objects are only available in server-side scripts, such as Business Rules and Script Includes. The GlideSystem object (gs) is also a server-side object that provides methods for logging, debugging, date and time calculations, etc.
Reference:
[GlideUser object (g_user)]
[Workflow scripts]
[Business Rules]
Script Includes
[GlideSystem object (gs)]

Application Access is a feature that allows you to control the access level of other application scopes to your application's data tables. By setting the Accessible from field value to This application scope only, you can restrict the access to your data tables to only your application scope. This means that other application scopes cannot create, read, write, or delete records on your data tables, unless they have explicit permissions through Access Controls or other means.
References:
* Application Access
* [Application scope]
https://developer.servicenow.com/dev.do#!/learn/learning-plans/rome/new_to_servicenow/app_store_learnv2_se
https://docs.servicenow.com/bundle/rome-application-development/page/build/applications/concept/c_ExampleD

https://developer.servicenow.com/dev.do#!/learn/courses/tokyo/app_store_learnv2_scripting_tokyo_scripting_in

To link a ServiceNow application to a Git repository, you need to provide the user name, URL, and password of the Git account that hosts the repository12. The URL is the address of the Git repository that you want to link to the application. The user name and password are the credentials that you use to access the Git account. Alternatively, you can use a personal access token instead of a password for increased security3.
Reference = 1: Link an application to source control - ServiceNow Docs 2: Publish an application to the application repository - ServiceNow 3: Linking an application to Git using a personal access token instead of a password - ServiceNow