What is Cross Site Request Forgery and how to defend against it?

The question can also be in two parts, in which case, candidates without knowledge of CSRF would get lost. If asked combined, candidates can guess that cross site request forgery is something that relates to malicious scripting with phishing intentions. The question may also be framed as “what is cross site request”. In this case, candidates cannot even guess that it is something malicious as the word ‘forgery’ is not there.