Let's get back to our EventStorming session and look at some part of our model.

There is a repetition on all those commands. Can you see it? All those commands are being executed on something that is called a Classified Ad. Also, if you recall all those conversations with domain experts, our team members frequently referred to this term when talking about the business in general and also about the model.

Mainly, we have an entity here. Entities represent unique objects of the same type. In addition to classified ads, we might expect our system to hold information about sellers and buyers, and those might be entities too, apart from being just roles in the system. It is because we need to identify those people, so we need to have something unique, like username or email address, to understand who is who. The same is valid for a classified ad. Imagine ads like this:

Both ads are the same if we ignore who is selling and for what price. But, most probably these are two different objects. Because of mass-production of IKEA, there is a significant chance that multiple similar used objects are being sold at the same time but for us those objects are different. It is because we are not using object properties, like model and size, to find out if two objects are identical. In our system, these objects will be represented in two different classified ads and will have a separate identity.