Applicant tracking system, or ATS, is a process software used by recruitments to improve efficiency of recruitment process.
It is a process management software used by recruitment teams to improve their efficiency.
It commonly provides features such as:
Biggest myth candidates have is, ATS uses some keyword matching and resumes that do not contain these keywords are automatically rejected.
This is not true. ATS is a tool to help recruiters manage their recruitment process, not to reject candidates.
If you have read through job description and are sure you qualify for it at even 50% level, apply for it. ATS will not reject you just because you did not use the right keywords.