E-R model provides a powerful tool for abstractly describing the real world. The conceptual model it represents is the basis of various data models, and all kinds of data submitted to the management information system are reflected in real form, which is convenient for data processing, analysis and processing, and finally get the information needed for decision-making!

I think E-R diagram and data flow diagram are two parallel analysis methods.

E-R diagram is commonly used in database analysis.

If you have to divide it, there are high and low.

E-R diagram, data flow diagram, data dictionary

For details, please refer to the professional books on information system development.