Is UnitOfWork equals Transaction? Or it is more than that?

The internet is full of information about UnitOfWork pattern; even SO is not an exception.

I still do not understand something about it. In my understanding UnitOfWork = Transaction in DB. Thats all; nothing more, nothing less.

Is this correct?

My confusion is due to how it is implemented in different ORMs. NHibernate uses ISession for more than just a Transaction. Dapper leaves everything to you.

My question here is about design pattern only without considering any ORM or technology.

If it is more than just Transaction, please explain how.