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.