What to show them
The machine
The words and phrases in the job description should be on your resume. The applicant tracking system will match the electronic version of your resume with the electronic version of the job description.
The administrative staff person
The staff person, who may not know much about the actual position, is also looking for key words but more importantly they are looking at the bold titles.
Highlight in chronological order, most recent first, companies you've worked for, dates of employment, dates of specific job titles and dates of education and degrees earned.
The Human Resources Manager
The HR Manager is interested in understanding why you want this job and whether you will be a good fit.
You need to make sure they can see "your story," i.e., your career progression where the next logical step is the job you're applying for.
The hiring manager
The hiring manager needs to see skills and experience relevant to what they need done.
Experience overcoming challenges similar to what the hiring manager faces will be the most valuable to show.