The Concatenate function concatenates a mix of individual strings and a single-column table of strings. When you use this function with individual strings, it's equivalent to using the & operator.
Reference:
https://learn.microsoft.com/en-us/power-platform/power-fx/reference/function-concatenate

Explanation:
Box 1: Custom connector
Register an app in the Azure Active Directory and request permission to use the right Graph API(s) and use this as custom connector.
Box 2: Microsoft Flow
The company already is implementing Power Apps in a Power Platform environment (which means model driven app will be there already), You need to implement other required components (other than model driven app so it would be Microsoft Flow aka Power Automate)
https://powerapps.microsoft.com/en-us/blog/implementing-role-based-permission/
https://www.encorebusiness.com/blog/powerapps-flow-can/

Explanation:
Box 1: Action
An action is something that occurs as a result of the workflow. For example, send an email or copy a file. In this case, the action is to retrieve the top five posts from a Facebook page.
Box 2: Action
An action is something that occurs as a result of the workflow. For example, send an email or copy a file. In this case, the action is to insert records into a database.
Box 3: Expression
Sometimes users just need to do basic operations like getting the current time, adding numbers together, or replacing a part of a string of text. That's possible inline in any flow action. Microsoft Flow leverages the same Workflow Definition Language used by Azure Logic apps. For new users who are unfamiliar with the expression language, there is an inline help experience that shows how to use each expression as they build out their flow.
Box 4: Trigger
A trigger is something that triggers or starts the workflow. It could be a new file uploaded to a document library, a new item created in the list or an email sent to your Inbox something that will start (kick-off the workflow).
There are two types of triggers:
- Automatic trigger is pre-programmed into the workflow based on a certain rule (i.e. new document or item created, email sent, etc.)
- Manual Trigger is a trigger initiated by a user. Unlike with automatic trigger above, the workflow will only start when initiated manually by the end user (for example, from the Document Library for a selected file). Manual trigger is only supported for certain types of workflows (i.e. Get feedback from your manager for the selected file) Reference:
https://sharepointmaven.com/3-major-components-microsoft-flow/
https://www.avepoint.com/blog/office-365/office-365-automation/
https://flow.microsoft.com/de-de/blog/use-expressions-in-actions/
https://docs.microsoft.com/en-us/power-automate/getting-started