In Django 5.1 difference between Model and AbstractUser

I am looking at the Django Documentation and am a bit confused as the differences between:

from django.contrib.auth.models import AbstractUser
from django.db.models import Model

I tried doing the following in a class and got an error that has to do with the following topic: Python multiple inheritance and MRO

The error emerged because I had done the following:

class Employee(Model, AbstractUser):
   pass

When I went to make migrations in Django, an error message said it violated MRO. When I searched what that meant on Google, I found a Stack Overflow post that mentions that it happens when it can't decide between the two classes, a specific value, or a method.

In my research, there might be a conflict amongst similar methods in class.

I am expecting to have an Employee that has a custom authentication, and is an entity in the database. How would I go about achieving this, do I have to pick AbstractUser over Model over using them both?

class Employee(AbstractUser):
   pass

# django.contrib.auth.models
class AbstractUser(AbstractBaseUser, PermissionsMixin):
    ...

# django.contrib.auth.base_user
class AbstractBaseUser(models.Model):
    ...