So could someone explain to me what weak entities are using simple crows foot erd diagrams?

Weak Entities

There are several entity types in which it is impossible to establish a key property, despite the fact that an entity type must have one to identify each entity in the entity set uniquely. These are referred to as the Weak Entity type.

• Weak entity sets have insufficient properties to generate a primary key, whereas strong entity sets are defined as having a primary key.
• Because the weak entities lack a primary key, they are unable to be recognized on their own and must rely on another entity for identification.
• Weak entities rely on strong entities to maintain their existence. 
• A double rectangle represents a weak entity. Double diamonds indicate the relationship between a strong and a weak entity.