How many candidates are interviewed for a job?

Excuse me, could you please clarify the process for selecting candidates for a job position? Specifically, how many candidates are typically interviewed for a single opening? Is there a standard number that companies adhere to, or does it vary depending on the nature of the job and the organization's hiring practices? Additionally, are there any specific criteria that determine whether a candidate progresses to the interview stage, or is it a more subjective process?