funding - What is a soft-money research position?

I have read the term "soft-money research position" a few times.

E.g. Path of a postdoc.

Another consideration for interviewees is whether to pursue a "soft-money" position. A tenure-track university professor is typically paid a nine-month salary to teach one or more courses, conduct research and train graduate students. During the summer months, the professor can optionally pay his or her salary from grant money. In contrast, non-tenure-track research professors often hold soft-money positions, which require them to cover 100 percent of their salary from research grants, teaching and/or administrative responsibilities. Soft-money positions offer the advantage of few teaching responsibilities, which frees time for grant writing and conducting research, but at the expense of job security, since winning grants is a necessity. The Hutchinson Center and some other private institutions offer a compromise between these systems, covering up to half of a faculty member's salary from institutional funds, so research grants only have to cover the remainder.

Advice for stats students on the academic job market gives a clear distinction between soft and hard money:

Before listing the options I should explain the concept of hard versus soft money. Revenue in academia comes from tuition (in public schools the state kicks in some extra $), external funding (e.g. NIH grants), services (e.g. patient care), and philanthropy (endowment). The money that comes from tuition, services, and philanthropy is referred to as hard money. Every year roughly the same amount is available and the way its split among departments rarely changes. When it does, it’s because your chair has either lost or won a long hard-fought zero-sum battle. Research money comes from NIH, NSF, DoD, etc.. and one has to write grants to raise funding (which pay part or all of your salary). These days about 10% of grant applications are funded, so it is certainly not guaranteed. Although at the school level the law of large numbers kicks in, at the individual level it certainly doesn’t. Note that the break down of revenue varies widely from institution to institution. Liberal arts colleges are almost 100% hard money while research institutes are almost 100% soft money.

I'm still confused regarding the exact definition of a soft-money research position: what is the threshold soft-money : hard-money above which a position is regarded as a soft-money position?

Conversely, what is a hard-money research position? Is it any research position that is not a soft-money research position?