On a resume affiliation means

Answer 1

It could mean multiple things. For example:

• Current and/or past memberships to organizations. This may also include serving on any committees and/or holding an office within that organization.
• Personal and/or business references

Now in my experience over years, I've found that when employer uses the word "affiliations," they generally mean "memberships."

On a resume affiliations means any professional connections related to the applicant job.