Maltego is the leading visual link-analysis tool for OSINT and infrastructure investigations. Analysts drag "entities" (a domain, an email, a person) onto a canvas and run transforms — queries against integrations (WHOIS, Shodan, HaveIBeenPwned, VirusTotal, social media) that pivot to new entities.
The graph reveals relationships that would be tedious to discover manually: shared hosting infrastructure, related domains under one registrant, email accounts breached together, etc.