When it its claimed that Windows and Linux Operating Systems are free from viruses, is it meant that no viruses have been written for them or that they have security measures that make them immune to viruses?

[Sonny]

Hello everyone, I have a strange problem, when it its claimed that windows and linux operating systems are free from viruses, is it meant that no viruses have been written for them or that they have security measures that make them immune to viruses? Please help me quickly.