Flat feet are the result of either how you developed growing up or may be the result of injury or disease.
Having flat feet on their own does not mean that you have a specific problem, so, please do not worry about having them. Equally, having flat feet may pre-dispose you to certain musculoskeletal injuries BUT it will also potentially prevent you getting other injuries.
Being screened for flat feet and assessed as to whether you might need insoles or orthotics is helpful, but I would not necessarily go straight to having orthotics just because your arch profile is lower.
Flat feet is a description for people with a low arch profile. It may be used interchangeably to describe people with a pronated foot type. A pronated foot type may have the foot functioning at an unusual angle, despite having a well shaped arch.