It's essentially where a bonus from your armour allows you to wear another armour piece, and so that first armour can't be removed.
Imagine I had a pair of boots that gave me 10 strength, and with that 10 strength, I could wear a helmet, that gave me 10 Intelligence and allowed me to wear other armour. If I were to take off my boots, my armour would fall apart, so they are essentially 'locked' by my skill points.
I would strongly suggest using your natural skill points as the bedrock of your build, and having the points they give as a boon rather than something to rely upon.
Comments on Profile Post by XavierEXE