A multi-process browser splits its work into separate operating-system processes, usually isolating web page rendering and JavaScript execution from more trusted browser components such as the UI, network handling, and password or profile management. This design assumes web content is untrusted and keeps it in a lower-privilege process.
This matters because browsers are frequent attack targets. If an attacker exploits a bug in a renderer or content process, the compromise is easier to contain than in a single-process browser. Security boundaries like process separation, sandboxing, and restricted privileges make it harder to turn one flaw into full system access. In real attacks, adversaries often try to chain a content-execution bug with a sandbox escape, privilege escalation, or information disclosure. Defenders rely on the same design to reduce blast radius and to make browser updates more effective when new vulnerabilities are found.