This is a very high level overview of SQLs v/s NoSQL v/s Graph (technically NoSQL) database use cases.

There is much much more to dig here, for ex; why and how does the Graph the based exactly handle inter-connectivity of data better than SQL DBs? What are the different models of Graph DBs and what to use when? How NoSQL DBs emulate the relational DB joins? etc.

However, without getting into the nitty-gritty of details, this is the TL;DR that you should keep in mind.

P.S: Might post a detailed blog that answer the previous questions later.