How can I use the Notion API to automate Notion? API

So, I've been trying to build my own task management system, and I've finally settled down at notion.

From what I understand of the Notion API, when code (that I have written) is triggered, the code goes and connects the "Integration" to the Notion "Database" and then proceeds to execute whatever code is in the file.

But what confuses me is since I want to automate stuff inside Notion itself, specifically, get the code to read a column from the database and add a specific tag to another column, I don't understand how I'm supposed to get the code to trigger from inside notion. I preferably don't want the code to keep running 24/7 in my laptop so that changes in the database can be detected, but at this point I have no idea how to trigger any code at all.

Any ideas/guides?