The document discusses different types of relationships that can exist between entities in a database management system. It defines binary relationships as those linking two entity types, such as Student-Course. Ternary relationships link three entity types, like Student-Course-Faculty. Unary relationships link an entity type to itself in a recursive manner. The cardinality of relationships refers to the number of instances of one entity type that can be related to another and can be one-to-one, one-to-many, many-to-one, or many-to-many. Relationships can have attributes and instances represented as ordered tuples or triples.