The offensive side
A Red Team Assessment is similar to a penetration test in many ways but is more targeted. The goal of the Red Team Assessment is NOT to find as many vulnerabilities as possible. The goal is to test the organization's detection and response capabilities. The red team will try to get in and access sensitive information in any way possible, as quietly as possible. The Red Team Assessment emulates a malicious actor targeting attacks and looking to avoid detection, similar to an Advanced Persistent Threat (APT). Red Team Assessments are also normally longer in duration that Penetration Tests. A Penetration Test often takes place over 1-2 weeks, whereas a Red Team Assessment could be over 3-4 weeks or longer, and often consists of multiple people.
A Red Team Assessment does not look for multiple vulnerabilities but for those vulnerabilities that will achieve their goals. The goals are often the same as Penetration Test. Methods used during a Red Team Assessment include Social Engineering (Physical and Electronic), Wireless, External, and more. A Red Team Assessment is NOT for everyone though and should be performed by organizations with mature security programs. These are organizations that often have penetration tests done, have patched most vulnerabilities, and have generally positive penetration test results.