How to properly validate model fields?

Question

Django

Can you please tell me how to properly validate model fields?
In the REST API, when updating model fields, you need to check these fields for correctness. I read about validaitors, but I don't understand how they work at all. I'm talking about the field parameter, for example

title = models.CharField(max_length=256, validaitors=[some_validation])

I installed these validators, but I don’t understand at what stage they should be called.
Tell me how to do it right through validators or maybe there is a better way.