Psychology Question - Primary vs Secondary Personality Types?

Yesterday, I was having a coffee with a psychologist friend of mine. We were discussing various subjects etc, and the question of human compatibility came up.

She mentioned the DISC system, and I’d like to learn more about this. I’m hoping I’ve got this right…

D Types - Dominant… always need to be the boss etc. Often overbearing. Very hard working.

I Types - People Persons - excellent minglers, lots of charisma, good management potential. Often are entertainers.

S Types - Teachers, priests, community oriented people. Driven to selflessness etc. Real worker types.

C Types - Analytical. Engineers, Architects, intellectually oriented. Superb workers in unsupervised roles.
Now, near as I remember, the theory goes like this (and I heartily welcome more feedback as needed…) apparently we all have our Primary Personality Type clearly identified by around 7 to 9 years of age - and it’s not hereditary. It’s seemingly as random as nature itself.

Our Secondary Personality Type is kinda like our “backup” personality - it’s who we are when we’re not being our “primary self”. Think of it as being “who we are” when we leave work.

It seems that we tend to be most compatible with people who’s Primary Personality Type matches our own Secondary Type. And vice verse. Often, especially in relationships - we come close - real close. That is, our partner’s Secondary Type is also our own Secondary Type and for a long time that will give us the perception of much common ground. But over time, if our Partner’s Primary Type is one which naturally clashes with our own Primary Type, then the relationship is destined to get tense and probably end.

Now, I’m happy to concede I might have got this all wrong. But I nonetheless find it really, REALLY interesting. Does anyone out there have more information on the DISC system? Or would they like to contribute to this thread.

I reckon we could share some interesting stuff.