From medium.com
What is Maltego and why use it for OSINT?
Maltego is a data mining tool that mines a variety of open-source data resources and uses that data to create graphs for analyzing connections. The graphs allow you to easily make connections between information such as name, email organizational structure, domains, documents, etc. Maltego uses Java so it can run on Windows, Mac, and Linux and is available in many OSINT Linux distros like Buscador or Kali. Basically, it will parse a large amount of information and search various open-source websites for you and then toss out a pretty looking graph that will help you put the pieces together. Maltego can be used as a resource at any point during the investigation however if your target is a domain it makes sense to start mapping the network with Maltego from the start.