auth: These are scripts related to user authentication.

broadcast: This is a very interesting category of scripts that uses broadcast petitions to gather information.

brute: This category of scripts helps conduct brute-force password auditing.

default: These are the scripts that are executed when a script scan is executed (-sC).

discovery: These are scripts related to host and service discovery.

dos: These scripts are related to denial-of-service attacks.

exploit: These are scripts that exploit security vulnerabilities.

external: This category is for scripts depending on a third-party service.

fuzzer: These are NSE scripts focused on fuzzing.

intrusive: This is a category for scripts that might crash something or generate a lot of network noise. Scripts that system administrators may consider intrusive go here.

malware: This is a category for scripts related to malware detection.

safe: These are scripts that are considered safe in all situations.

version: These are scripts used in advanced versioning.

vuln: These are scripts related to security vulnerabilities.