The document discusses entity relationship data modeling, which visually represents how data is related. It defines key concepts like entities (objects like people or places), attributes (properties of entities), relationships (connections between entities), and relationship types (one-to-one, one-to-many, many-to-one, many-to-many). Symbols are used to depict these elements on an entity relationship diagram, including rectangles for entities, ovals for attributes, diamonds for relationships, and lines for links. Weak entities, composite attributes, and recursive relationships are also summarized.