Soft skills are fundamentally the personality traits of a person and how s/he utilizes it to develop their inter-personal relationships. This is a subjective term and encompasses a variety of qualities such as communication skills, emotional intelligence, leadership, teamwork, etc.
The skills required may vary depending on the nature of the job. Certain skills may be highly pertinent for one job, but not for another. For example, however technically brilliant a doctor might be, without patience and approachability, s/he would not be efficient. It applies to almost all professions. A salesman should have excellent communication skills to convince and comfort the customer, a team leader must have good leadership and management skills, a content writer must be flexible and creative, and so on.