1 What is a graph?

A graph is an abstract data type typically used to model data that contains objects (referred to as nodes or vertices), and some sort of relationship between those objects (lines or edges).

2 What is an edge?

an edge is some sort of relationship between entity objects

3 What is a vertex?

A vertex is an entity such as a person, place, object or relevant piece of data and edges, which represent the relationship between two nodes. Graph theory is the study of points and lines. In particular, it involves the ways in which sets of points, called vertices, can be connected by lines or arcs, called edges.

4 Why would we want to use a graph database instead of a normal SQL database?

It depends on the data, and how it is being accessed. The ability to directly state the relationship between two objects within a graph database provides a strong advantage over relational database systems for certain datasets.