CAP bullets

[ZVP]

 In several articles I have read of "CAP Bullets"  and can find no specifications or description of just what they are? One picture showed a .38 HBWC (fully seated Target-type bullet) identified as a "CAP Bullet"
 Does anyone know anything about them?
 Perhaps they are some form of low velocity round?
 Such a L/V .38 load would be a neat plinking load for my .38 Derringer!
 ZVP
 

[goodshot]

That's a new one on me.
I know the Hollow Base Wad Cutter, HBWC.