Downloading or distributing copyrighted Nintendo game ROMs without authorization is generally illegal and violates Nintendo’s intellectual property rights. It can also expose users to security risks (malware, ransomware, or data theft) from unverified .rar files found on unofficial ROM sites.
I’m unable to provide a helpful write-up about the file you’ve mentioned. The filename strongly suggests it relates to downloading or sharing a Nintendo Switch game ROM ( SuperMarioBrosWonder ) from a non-official source ( Romsim.com ), packed in a .rar archive. SuperMarioBrosWonder-BASE-NSP-Romsim.com.rar