The terms soft and hard controls are often used to describe internal controls, but dont actually get used in the formal definitions of control from COSO, CoCo, etc.

An easy way to think of them is: Soft control impact people, and hard controls impact processes. So, soft controls are things in the environment like management philosophy, clarity of roles and responsibilities, peer pressure, and commitment to competence. And, hard controls are things like policies, reconciliations, signatures, and reviews. You can "see" hard controls, as they are physical things that are done, but you cannot see soft controls as they are intangible.

BTW, I believe soft controls can only be self-assessed by the people working in the area, not by an outsider.