OOP what is the difference between the pattern activerecord and ORM?

The question is incorrectly formulated.

AR is ORM, one of the options for implementation.
That is, the question sounds like "how does a Mercedes differ from a car".

If we talk about any differences, we usually mean two variants of the implementation of ORM - Active Record and Data Mapper. They differ only in that in AR methods of working with the database are stored in the object itself, and in the DM - separately. As a result, the latter is considered more academically correct (sharing of responsibility) and provides more advantages in complex projects. Examples of AR implementations are Yii AR and Eloquent, DM - Doctrine and Atlas.Orm.