These show how entities are related to each other – they may either be represented with diamonds, or written as text on the connector between the two entities.
In the first style of diagram, you can see that both User and Coach write comments, and the User can perform a habit Checkin, these two ‘actions’ aren’t represented at all in the second style of diagram, which purely represents the data, not any interactions.
Relationship connectors use Crow’s foot notation to show how many of each entity is related to another entity. For example, in the Habit Tracker app – A Coach can have 0 to many Users, but a User can only have 0 or 1 Coach. Users may have many Habits, and each Habit may belong to many users.
Tip: Hover over each shape in the Entity Relation library to see what type it is.