Pipeline is not triggered for the Pull Request on Azure DevOps Pipeline

I am working on such scenario:

1. Run pipeline when commits are pushed from specific branches.
2. Only allow to run pipeline when PR is made for main.

That configuration triggers the pipeline when I made the PR to main:

name: CI-$(Date:dd.MM.yyyy)

trigger:
  branches:
    include:
      - main
      - develop
      - release

pr:
  branches:
    include:
      - main

pool:
  name: $(agent)

# Rest of the code

When I remove main keyword from trigger section and keep the pr section pipeline does not start after the PR is made to main. Tried to review docs and other similar topic, but nothing found.

Also, when I commented all trigger section and keep the pr, made a commit I see the pipeline works. It shouldn't because it was just a commit, not a pr.

EDIT 1.

Based on the first reply, and above documentation, lets say I am going to create it according to that screenshot:

It means that I can remove completely the pr section from my pipeline? And the rest should be untouched. Sorry for additional question, but I did it like on the attached screenshot from main branch, than create a pr to main and pipeline does not trigger (with removed pr section and leave trigger only). Of course before I pushed that pipeline to the main branch, create the first pipeline based on provided .yml and run first time the new pipeline manually just to check if it works, and it does. Than test with pr does not trigger the pipeline.

As per pr definition:

YAML PR triggers are supported only in GitHub and Bitbucket Cloud.

If you use Azure Repos Git, you can configure a branch policy for build validation to trigger your build pipeline for validation.