In a graph database, a node represents an entity or data point. Nodes are used to store and represent individual entities, and relationships between nodes express the connections or associations between these entities. This allows for a flexible and efficient representation of complex relationships in data.

In specialization, "subtypes" refer to the specialized entities that are derived from a more generalized entity. These subtypes inherit the attributes and relationships of the parent entity but may also have unique characteristics specific to their subtype.

The fundamental data structure used in a Key-Value Store is a Hash Table. Hash Tables provide efficient key-based access to values by mapping keys to specific locations in the table. This allows for quick retrieval of values based on their associated keys.

In an ERD, an entity represents a real-world object or concept, such as a person, place, thing, or event, about which data is stored in a database. Entities are typically nouns and serve as the foundation for the structure of the database. Entities are depicted as rectangles in an ERD.

Reverse Engineering helps in understanding the existing database schema by documenting its structure and relationships. This facilitates database documentation, making it easier for developers and database administrators to comprehend and work with the database.

Detailed Primary integrity ensures that primary key values are unique and not null. The primary key is a crucial component in a relational database as it uniquely identifies each record in a table, preventing duplication and ensuring data reliability.

Using compression techniques in data storage systems provides the advantage of reduced storage space requirements. This leads to more efficient use of storage resources, cost savings, and improved overall system performance. Additionally, it can contribute to faster data transmission, especially in scenarios involving data transfer over networks.

In a superclass-subclass relationship, a Subtype is a specialized version of a more general entity, known as the superclass. This modeling concept allows for creating a hierarchy within entities, emphasizing shared and distinct attributes.

ACID stands for Atomicity, Consistency, Isolation, and Durability. These are the four key properties that guarantee the reliability of transactions in a database system.

Common methods used to monitor database performance include utilizing database performance counters to track key metrics, implementing query profiling to analyze query execution patterns, and employing specialized database monitoring tools to monitor system health and performance in real-time. These methods help identify performance bottlenecks and optimize database operations.