An E-R model maps real-life things as entities and their properties as attributes. Every entity in the E-R model is related to some other entity. The relation between theses entities defines how each entity is related to other entities. This forms an E-R model. An E-R model can be mapped to a relational model using foreign keys. Entities are tables and attributes becomes columns of that table. All these tables can, then, be related using foreign keys.