ER diagrams are used to analyze existing databases to find and resolve problems in logic or deployment. Drawing the diagram should reveal where it's going wrong. Business information systems: The diagrams are used to design or analyze relational databases used in business processes.

A database schema represents the logical configuration of all or part of a relational database. It can exist both as a visual representation and as a set of formulas. It is an easy to use graphical tool for modeling data. Widely used in Database Design. It is a GUI representation of the logical structure of a Database. It helps you to identifies the entities which exist in a system and the relationships between those entities.

An entity relationship diagram (ERD) shows the relationships of entity sets stored in a database. ... By defining the entities, their attributes, and showing the relationships between them, an ER diagram illustrates the logical structure of databases. ER diagrams are used to sketch out the design of a database.
A schema in psychology and other social sciences describes a mental concept. It provides information to an individual about what to expect from diverse experiences and circumstances. These schemas are developed and based on life experiences and provide a guide to one's cognitive processes and behavior.