data with a clear schema

table like structures for flexible data without the need of joins

storing large volumes of data at extreme write speeds where data has no consistent schema

if you want to find the optimal route between railway stations

extremely fast access by use of a key

if you want to find out relations between persons for example by means of a path

they are the simplest NoSQL database

search for data with an arbitrary complex structure (e.g. structure contains substructure contains substructure, ...)

JSON data

works with nodes and edges

Relationships between data has the same importance as data itself and give additional information. Relations are called edges then

search for data with SQL as query language