and yep, Chin Na is a collection of techniques that are basically, grabs, holds, releases, locks, etc.
generally they are defensive in nature and are drawn from techniques within a given style or system.
there is a very, very large variety of these techniques.
pressure points are another thing. Some chin na techs employ pressure points in their usage.
pressure points can be used to damage or to heal.
also, a collection of techniques that are not inherently a system except that the healing aspects may be considered a system as in: acupunture/acupressure.
if the term is used in context to dim mak/dan xiue, then it is a body of knowledge (system) concerning striking points to be used in fighting.
I’d go a step further. Chin na is one of the expressions of the core of Chinese Martial Arts. Chin na works when you can read the flow of energy. Many people don’t work this aspect of CMA.
As many have said it is part of your arsenal that can be used in conjunction with various techniques. i.e we have chinafa from eagle claw and shuai chaio so when defending ourselfs we would block a punch, strike back while joint locking follow up with a throw that either breaks or damages the limb during execution or by the throw itself. But if you took the joint lock out of the scenario the result would be incomplete.