What's the "applicant tracking system?" Why would companies track their candidates?

Native speaker’s answer
Rebecca
An "applicant tracking system" or "ATS" is a computer software that's supposed to pick up keywords that are needed for a job role or description. This happens before humans see them, and it lessens the workload to focus on the people who could actually benefit the workplace. It's probably necessary since, in this day and age of technology, hundreds or thousands of people could apply for the same job online, and not all of them may fit the description.