What is Jing?
I've heard Jing described a whole lot of ways; it's super-Ki, it's cleansed Ki, advanced Ki, a whole different energy made out of Ki, and of course, condensed Ki.
It's a fair mix of those things. All Ki contains some amount of Jing, this is what allows it to have affects outside of the immediate vicinity of our bodies, however only a very small amount of Ki is Jing, which is why Ki has a tendency to break down if it's away from the body and you're not concentrating on it. The Jing in Ki is what makes Ki different from Mana; both are life energy but only one has that Force in it.
So where do people get the idea that it's compressed or condensed Ki? If you try to compress your Ki, you end up pushing out everything except the Jing. This makes Jing as a usable substance (like in a Jing Ball) both very powerful and very hard to control. It's 100% Force of Ki, but Jing isn't meant to exist like that. Much like the artificial elements scientists have created Jing is unstable in this state and will break down. This causes it to be somewhat volatile and there is a much greater chance of burnout while practicing with Jing.
How do I make Jing?
The best way to make a Ki Ball and compress it. I've found that the best way is to make a really big soft Ki Ball. I then make a hard layer around it using either Ki or Psi, depending on which I feel in the mood for. I then shrink this outer layer down until most of the Ki inside is crushed out. I then repeat the process by making a big Ki Ball again, this time around my little ball of Jing. This method takes lots of concentration but is the best method of creating a large amount of Jing. If you have trouble with that one then try just making a normal Ki Ball and just keep putting in more and more Ki but don't let it grow in size. This method will produce a ball which has lots of Jing and may even be mostly Jing, but creating a ball of pure Jing through this method is very difficult. Once you're experienced you'll be able to make Jing by continually flowing Ki down your shoulders and out your hands through your bones, using the rest of the Ki in your arms to squeeze the bones so tight that the Jing cannot pass through. This will leave your bones full of Jing. Always use any pure Jing you have inside your body as it's not good for you to keep it in that state.
How does that tech work?
Imagine that you have a bucket you want full of dirt, and you're going to fill it using some very watery mud. You will fill the bucket with this mud and wait for the water to evaporate. This would leave the bucket about half full of dirt, and half empty because the other half evaporated. So you fill that remaining half with more mud and the same thing happens, so now it's about three quarters full.
You're doing a very similar thing with Ki when you make Jing. You're squeezing out the part that sustains life, the part that heals, and all other parts that aren't used for combat (just like you're letting everything that isn't dirt evaporate). All those other things took up space in the original Ki ball you made in your chest, so when you squeeze them out the resulting ball of Jing is much smaller (like how the bucket that was 100% full when it was mud is only 50% full when the water evaporates), so you have to pull in more Ki, squeeze it, etc.
Can I make Jing for the other aspects of Ki?
Probably, but they wouldn't be very useful. Jing made of nothing but the healing aspect wouldn't be good for healing any more. Healing someone with Jing, even if it were made from the healing aspect, would be like taking a month's worth of medication all at once - you would effectively overdose. Similar thing with the aspect of Ki used to sustain life. It would be like putting a big battery in something that requires a small battery - you would fry the thing by over-charging it. Ki isn't meant to exist as Jing. The nature of Ki is to be balanced, and maintaining it in this altered state takes practice and skill
Is Jing a type of Ki or is it a separate energy?
Is ice water? Jing is both, really. It's a type of Ki in that 100% of it is Ki, just as ice is 100% made of water. Jing is also a separate energy in a way because it has distinctively different attributes than Ki, just as ice has the distinctively different attribute of existing as a completely different state of matter (solid) than water (liquid).
So is Jing a type of Ki? That depends entirely on if you feel that ice is water.
I heard that "Jing" means semen...
Such is the problem with Chinese. Chinese is a tonal language. That means that pauses mid-syllable, how long vowels are drawn out, and the pitch of the word actually decide it's meaning. There are over 5 ways to pronounce "Chi" and each of them has a different meaning. In addition to this, there are lots of misinterpretations of terms and meaning even when the translation was correct!
From Wikipedia article Jing (TCM)
Production of semen, in the man, and menstrual blood (or pregnancy), in the woman, are believed to place the biggest strains on jing. Because of this, some even equate jing with semen, but this is inaccurate; the jing circulates through the 8 extraordinary vessels and creates marrow and semen, among other functions.
What it doesn't mention is that the Jing flowing through you is not actualized, running through you as part of your Ki. In reality, little was known about Jing in ancient China. How could the understand an energy they never worked with heavily? They have the principles right, but little else.