Discuss how a graph database can be useful to implement specific features in hypothetical or real social network

It is database that uses graph structure with nodes,edges and properties to represent and store data.

It is a type of NoSQL database, created to overcome relational database limitations.
It is powerful tool for graph queries.

Components of Graph database :
Nodes : These are the entities of the graph. It can hold any number of attributes called properties.
Relationship : It provide directed, named, semantically relevant connections between the nodes. Relationship always has a direction, a type, a start node and a end node.
Properties are information of associated nodes

Graph models : 
Labeled property graph
Resource Description Framework

There are multiple types of graph types which are broadly categorized as five types:
Social graph
Intent graph
Consumption graph
Interest graph
Mobile graph