The Data Access Layer (DAL) is the layer of a system that exists between the business logic layer and the persistence / storage layer.

A DAL might be a single class, or it might be composed of multiple Data Access Objects (DAOs).

It may have a facade over the top for the business layer to talk to, hiding the complexity of the data access logic.

It might be a third-party object-relational mapping tool (ORM) such as Hibernate.

DAL is an architectural term, DAOs are a design detail.