What does ATS-optimised mean and do I need to pay attention to it?

ATS stands for Applicant Tracking System — software that automatically manages and pre-screens applications. ATS-optimised means: machine-readable formatting (no table-based CV, no photo as main content), keywords from the job posting, clear section headings. In Germany's Mittelstand, ATS is less common than in large corporations, but the trend is clearly moving towards automation.