Resume scanning is the process used by the hiring company to go through resumes and check for basic requirements. People who meet the basic requirements are then called for the first round of interviews.
This process nowadays is conducted digitally using an ATS, Applicant Tracking System, which specifically looks for keywords and certain expressions on whose basis the selection is made. These keywords and expressions are mostly skills, basic certification, or experience that the candidate is required to have.
Clearing this scanning process is extremely important to land an interview, thus using the necessary keywords in the proper format is resume scanning.