What is Black Moon Lilith in retrograde?

I've looked through a Google search, I've searched on here (not thoroughly, mind you. I do not have the patience for it today and I know I'll forget about my question by the time I do have patience) but couldn't find anything.

I have both my Lilith and Black Moon Lilith Rx in Gemini in the 12th house, the former at 0 degrees in both the sign and the house, while the latter is 5 degrees.

Black Moon Lilith is square my Mars in Virgo in the 3rd house, square Saturn and Moon in Pisces in 9th, opposite Jupiter in Sagittarius in 6th. I read on a website I can't remember the name of, that it's a sore spot for Black Moon Lilith to be in harsh aspect to Mars and Saturn. Can anyone tell me why that is and that means in my chart?
My Black Moon Lilith has no harmonious aspects to it at all, I also wonder what that might mean.

But my main question is what does it mean to be retrograde? Is it too tall of any order to get an answer on what it means to be retrograde in that house and sign with those aspects? (Also how can a hypothetical point go retrograde?)