Dashboards show data from source reports as visual components that provide a snapshot of key metrics and performance indicators. Dashboards need to be refreshed manually or scheduled to run on a regular basis to reflect the most recent data from the reports. The running user of a dashboard determines whose security settings are applied when the dashboard is run. If the running user is different from the viewer of the dashboard, they may see different data based on their permissions and sharing settings. References:
https://trailhead.salesforce.com/en/content/learn/modules/lex_implementation_dashboards_and_reports/dashboar

Account teams are groups of users who work together on an account. You can enable account teams in Setup and assign team roles and access levels for each team member. Users can set up a default account team that is automatically added to any account that they own or create. This makes it easier for teams to collaborate with the same customer without manually sharing each account. References:
https://help.salesforce.com/s/articleView?id=sf.accountteam.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.accountteam_default.htm&type=5

To use as an identifier when importing and updating records from a separate system, an administrator should use External ID field type on an object. External ID fields allow storing unique identifiers from external systems and using them for matching records during import or update operations. External ID fields can also be used for upsert operations that insert new records or update existing ones based on external ID values. For example, an administrator can create an External ID field on Account object that stores account numbers from an external ERP system and use it for importing or updating accounts from that system. Rich Text field, Record ID, and Auto-Number field are not suitable for using as identifiers when importing and updating records from a separate system. References:
https://help.salesforce.com/s/articleView?id=sf.fields_about_field_types.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.data_loader_upsert.htm&type=5

To make a quick action available on the Salesforce mobile app, you need to add it to the Salesforce Mobile and Lightning Experience Actions section of the page layout. You can use the Page Layout Editor to drag and drop the quick action onto the section.
References: https://help.salesforce.com/s/articleView?id=sf.actions_in_lex.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.customize_page_layouts.htm&type=5

Page layout and field level security are two factors that determine whether a user can see a new field on a record. To troubleshoot this issue, the administrator should ensure that the page layout for the user's profile has been updated to include the new field and that the field level security of the field for the user profile allows read or edit access. References:
https://help.salesforce.com/s/articleView?id=sf.customize_layoutoverview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.admin_fls.htm&type=5